The Mystery of the Plumed Serpent

A KEN HOLT Mystery, No. 17

By Bruce Campbell

CHAPTER I

A ROUGH WELCOME

The big Allen kitchen was filled with the rich aroma of roasting meat. When Mom Allen opened the oven door to test the potatoes baking inside, the smell of good food grew even stronger.

Sandy Allen groaned in mock anguish from the stool on which he had perched his better-than-six-foot length. "Mom, please! Shut that oven door!" he pleaded. "How much more of that smell do you think I can stand-with nothing but cookies to eat?"

He was reaching toward the cookie bowl again when his mother pushed his hand away. "Stop nibbling!" she commanded. "You'll spoil your appetite."

"Hah!" The loud snort of disbelief came from the other side of the room, where Ken Holt sat astride a chair. "The day Sandy loses his appetite, the law of gravity will be repealed. Now I'm different," he went on, getting up and stretching his lean body. "I need all the nourishment I can force down. And I know you want me to build up my strength before we leave on our Mexican vacation next week."

He had his own hand near the cookies when Mom whisked the half-empty bowl out of his reach and transferred it to her worktable near the oven. An instant later, she picked the bowl up again, at the sight of her husband and older son coming through the kitchen door. "You get enough to eat at regular mealtimes, all of you," she said firmly, putting the bowl inside a cupboard and shutting the door.

"That's not fair!" Pop Allen protested. He looked down at his wife, whose head barely reached his shoulder. "These two chow hounds have been at those cookies for the past hour, and we haven't had a one-have we, Bert?"

Mom spoke before Bert had a chance to answer. "Judging from the continuous cracking of nuts I've been hearing, I doubt if either of you will collapse from hunger for a while."

"Nuts!" Bert eyed her in pretended amazement, and then nodded as if in sudden understanding. "You must mean the crackling gunfire on that television western we've been watching."

Mom reached up and disentangled a fragment of walnut shell from Bert's fuzzy sweater. "You should be more careful about getting in the way of stray bullets," she told him.

Sandy grinned at his older brother. "You should at least be more careful about the stories you try to get away with."

"Come on back to the living room, Bert," Pop said sympathetically. "If we're going to starve to death, we might as well do it in comfort."

"Oh, for goodness sake!" Mom said tartly. "Here it is only-" She eyed the kitchen clock. "My! It is almost seven, isn't it? What do you suppose has happened to that boy?" A note of anxiety had crept into her voice with the last words. "For all we know he's nothing but a child," she went on. "A poor, lone child in a strange land, perhaps unable to speak the language-"

"Now, Mom!" Pop protested.

"He wrote a letter in perfectly good English, Mom," Ken pointed out. "So he must be able to speak it pretty well, too."

"And you can scarcely say he's in a strange land, when he's already been in the United States for ten months," Sandy added.

"And if the Mexican government thought he deserved a scholarship, and sent him up here on his own," Bert put in, "he must be at least past kindergarten age and pretty well able to look after himself. So I think," he went on, winking at the others, "that we ought to go on with dinner, and let Ricardo Montez-"

"We will do nothing of the sort," his mother broke in. "The very idea! Imagine a guest arriving here for his first visit, and finding-" Then she realized that the others were all grinning at her, and she broke off. "But I do wish he'd arrive, and put my mind at rest," she added. "Tell me again what his letter said about the bus he'd take, Ken."

"He said he'd be on the bus leaving New York at as close to three as possible," Ken reminded her. "And since the buses leave on the half hour, and he wasn't on the one that left at two thirty, I suppose that means he'll be on the one that left at three thirty. And that bus usually gets here just about seven. It's too bad we didn't have time to get a letter back to him, telling him about the schedule and what Brentwood stop to get off at. As it is, well have to wait for his phone call."

"If it doesn't come within the next few minutes, Ken," Sandy said, "you'll have to go alone to pick up Ricardo. I just won't have the strength."

"Get along into the living room-all of you," Mom ordered. "You'll wheedle no more cookies out of me, nor anything else, until we sit down to dinner."

Pop shook his head. "She worries about strangers," he said, as if to himself, "but she can let her own menfolks suffer from malnutrition, vitamin deficiency-"

"Out!" Mom said.

They went, Ken leading the way, the three tall redheaded Allens following.

Ken often remembered vividly, as he did at this moment, the first time he had set eyes on the big-bodied, bighearted Allen clan. He had stumbled into the office of the Brentwood Advance, in desperate need of a hiding place from a pair of gangsters who had already kidnapped his father, Richard Holt, the foreign correspondent. Immediately the Allens had made his trouble their own, and had helped bring about the conclusion of the adventure they all afterward thought of as The Mystery of Skeleton Island.

Before that time, Ken, motherless since childhood, had lived in a succession of boarding schools while his father roamed the world on assignments for Global News Service. Since then, Ken had been a part of the Allen household, and he and Sandy had been as close as brothers. They worked together, too, as a highly efficient reporting team, Ken writing the news stories, Sandy illustrating them with his photographs. Pop Allen, exacting editor of the weekly Advance, sometimes admitted that they had the makings of real newsmen. Steven Granger, hard-boiled eastern manager of Global News, never put his praise into words, but he too had bought and used the boys' stories. Frequently those stories were accounts of adventures in which the boys themselves had been involved.

One of those adventures-the one they referred to as The Mystery of the Green Flame-came into Ken's mind now, because it had taken them to Mexico and brought them the friendship of a young Mexican boy, Roberto Rosario. It had been through Roberto that they had heard of Ricardo Montez, for whom Ken, the Allens-and Mom's dinner-were now waiting.

Roberto had appointed himself the boys' guide in the city of Rio Claro, and thus became innocently involved in the pitched battle that climaxed The Mystery of the Green Flame. When they returned home from Mexico, he wrote them occasional letters, carefully expressed in the English he was learning in school and from every tourist with whom he could scrape up a conversation.

In one of those letters, some ten months old now, Roberto had written, "You will not be angry, I think, if I tell you I have ask Ricardo Montez to visit with you. He has house next to mine in Rio Claro. His mother is cook at hotel. His father is dead long time. Ricardo is very smart. He is going to your country to learn how to be good farmer. I tell him to see you, or write letter, or speak by means of telephone. He is my most good friend, and you are my most good friends. So, you and Ricardo will also be most good friends. No?"

With the help of the Spanish dictionary they always needed when writing to Roberto, or to the Mexican police chief who had also become their friend during that same trip, Ken and Sandy had answered the letter. They urged Roberto to tell Ricardo Montez to get in touch with them as soon as he reached the United States.

But months had gone by and they had heard nothing. They hadn't worried because they had assumed that the young Mexican student had been too busy to write. Then, only a few days before, when Ken had been on the point of reporting this to Roberto, and telling him at the same time that they were planning a Mexican vacation and hoped to see him again, a note from Ricardo Montez arrived. It was brief and awkward. It asked if the writer might call on them before he returned to Mexico.

Ken and Sandy had replied swiftly, inviting the Mexican to Brentwood. Ricardo's answer to that letter was still in Ken's pocket.

He took it out now and looked at it again, while Sandy prowled restlessly up and down the living room, and Pop and Bert buried themselves among the several New York and Philadelphia papers they always read from cover to cover.

"Dear Ken and Sandy," Ricardo had written, "I am most grateful for your kind invitation. My school-work will be completed by March first. On March third I will travel by bus to the city of New York. There I will board a bus to Brentwood. I will take the bus which leaves for your town at the hour closest to three o'clock. When I reach Brentwood I will speak to you by telephone and tell you I have arrived.

"I am most happy to learn that you plan to visit in my country very soon. I will be most pleased if I can be of help to you in planning your trip, or after you arrive in Mexico.

"It is a shame to me that I have not conveyed my respects to Roberto's good friends at a much earlier time than this. My excuse is that I do not wish to impose on people who do not at all know me. But now I find that I cannot return to Rio Claro without consulting with you. So may I again say I am most grateful for your kind invitation to visit Brentwood."

As he read the final paragraph Ken felt once more the faint stir of concern the letter had given him on his first quick perusal. He had spoken to Sandy about it then.

"Doesn't this letter give you the feeling that Ricardo is in some sort of trouble?" Ken had said. "His reference to 'consulting' with us makes me feel he needs help."

Sandy had grinned. "He probably still needs a little help with his English, that's all. He thinks 'consult' means 'talk with'-and he's trying to say he won't be able to face Roberto without having at least talked with us."

"Maybe," Ken had admitted.

"Think of the confusion we probably create in Roberto's mind every time we write him in our feeble Spanish," Sandy had added.

Ken had grinned then too. "Yes, I suppose we do," he'd said.

The sharp ringing of the telephone cut into Ken's thoughts.

"At last!" Sandy said. "Our guest has arrived. Now we'll be able to eat" He started toward the phone.

But Ken was closer and picked it up first.

"Hello. Ricardo?" he said. "Is that you, Ricardo? This is Ken Holt." He paused a moment and then said, "Oh, Joe. Sorry. I was expecting- What? . . . Say that again-slower."

Out of the corner of his eye he saw Pop reach automatically for a pencil, and knew the others in the room had caught the note of alarm in his voice.

They were all watching him, and Mom had come to stand in the door of the living room, by the time he said, "Yes, I got it. ... Sure, we'll be right there- as fast as we can." He dropped the phone into its cradle.

"What's wrong, Ken?" Mom asked quickly.

"I'm sure it's nothing serious," Ken told her, trying to be reassuring. "That was Joe Meyers, down at the gas station-the one on the corner where the out-of-town buses stop. Ricardo's there-just got off the bus a minute ago. And Joe says he really isn't hurt."

"Hurt!" Mom repeated. "You mean there was an accident?"

"Not exactly," Ken said. "But it seems that-according to Joe-a car stopped alongside Ricardo the minute the bus pulled away, leaving him beside the road right across from Joe’s station. Then two men got out of the car and-well, Joe says they attacked Ricardo-knocked him down and started to beat him up."

CHAPTER II

RICARDO REPORTS

All four Allens stared at Ken in shocked silence for a moment.

"Attacked him!" Sandy said then. "But what-?"

"That poor boy!” Mom said. "Go get him right this minute! Hurry up! I'll phone Dr. Saunders and have him here by the time you-"

Pop interrupted her gently. "Take it easy, Mom. If Joe Meyers said the boy wasn't really hurt, I think we can wait until we see him before we call up the medical reserves. But phone us from Joe's if there's anything we should do before you get back here," he called after the boys, as Ken and Sandy went through the door on the way to their car.

Sandy slid behind the wheel. Ken had barely shut the right-hand door of their red convertible before the engine came to life. Sandy flipped into reverse and backed the car down the driveway into the quiet Brentwood street, already dark under a pale spring moon.

"Is that all Joe said?" Sandy demanded.

"That was it," Ken assured him. "Joe noticed the bus pull up, saw it pull away again, noticed that one passenger had gotten out. Then the passenger was hidden by a car that must have been coming along right behind the bus. The car stopped too, and the men in it got out. I gather it took Joe a minute to realize what they were doing to Ricardo." Ken braced himself against the swerve of the car as Sandy swung onto the curved highway approach. Almost immediately ahead of them, they could see the bright lights of Joe's service station.

"And then what?" Sandy was asking.

"Then Joe started across the highway to break it up," Ken said. "Just how he did it I'm not sure. But we'll get the whole story in a minute."

Sandy braked to a hard stop right beside the open door of Joe's office. They were out of the car an instant later, and entering the small room.

A slight, black-haired stranger, sitting on a carton alongside the water cooler, started to his feet at the sight of them. A sudden smile showed teeth that looked very white against the tan of his skin.

"Ken? Sandy?" the stranger said. "I am Ricardo Montez."

They were beside him while he was still speaking, Ken anxiously feeling one slender arm in the light jacket, Sandy the other.

"Hello, Ricardo," Ken said. "Yes, I'm Ken-and this is Sandy. Are you really all right?" He stepped back then, and looked the short, slim figure up and down.

"Si, si-yes," Ricardo assured them earnestly. "I am not hurt. I did not want Mr. Meyers to tell you what happened, but-"

"Look at your coat!" Sandy exclaimed, fingering a tear that started at the pocket of Ricardo's jacket and ran down a ragged six inches.

"But that is the only damage," Ricardo said. "That, and one button pulled out from my shirt. It is nothing, please. Your good friend came very quickly to help me, and-"

He broke off as the big figure of Joe Meyers appeared in the doorway of the greasing section of his station.

"I sure came as fast as I could," Joe said. "How do you like that, anyway?" he demanded of Ken and Sandy. "A couple of cheap hoodlums thinking they could get away with a holdup right across the highway from my service station! At least I chased them off before they got anything. I was waving a big wrench as I ran across the road. One of them sees me coming, grabs the other-and they're in their car and taking off before you can say Jack Robinson."

"They really didn't get anything, Ricardo?" Ken asked. "They didn't take your money?"

"No. I had no- No, they took nothing," Ricardo said. "I think they were very scared when they see Mr. Meyers," he added quickly. "They did not take my bag, you see." He pointed to the battered suitcase standing a few feet away.

Ken had caught the pause and the sudden shift in Ricardo's words. Suddenly he was quite sure why Ricardo had wanted to "consult" with Sandy and himself. He was equally sure that Ricardo had been on the point of confessing that he had no money to steal and had changed his mind because of Joe Meyers' presence. Quickly Ken changed the subject. "Had you ever seen the two men before, Ricardo?" he asked.

"No. Never," Ricardo assured him. "When they first stopped beside me, I thought they wanted to ask me a question-how to find a certain house, perhaps. But they did not speak. One man jumped out and began to fight with me. The other jumped out to help him. I fought back, but they are two and I am only one, and not so big as they. I was on the ground very fast. And then your friend came." He smiled gratefully at Joe.

"I'm just glad I wasn't under the lift-greasing a car, or something," Joe said. "Then I wouldn't have seen them right away. But I was standing right inside the door here. They could have seen me if they'd looked over this way. What I can't understand is why they didn't. They must be amateurs at this business, taking a risk like that."

"I don't suppose you got the number of their car?" Sandy said.

"I'm telling you, they took off like a rocket before I even got across the road," Joe said disgustedly.

"And you didn't see the car license number either, did you, Ricardo?" Ken asked.

"I saw nothing-not even the faces of the men," Ricardo said. "Their hats were down like this." He gestured vividly with a slim hand. "And everything happened so fast."

"Sure," Ken said sympathetically. "And now I think we ought to get you home fast, before Mom comes down here with a stretcher."

"A stretcher?" Ricardo looked puzzled. It was the first English word that had stumped him, though his own English had an unmistakable accent, and he sometimes paused momentarily as if searching for the phrase he needed.

They all laughed.

"Don't worry, kid," Joe said. "As long as you don't need one, there's nothing to worry about."

"I guess I would have much to worry about, if you had not helped me," Ricardo said.

"Think nothing of it," Joe assured him. "Cars greased, flats fixed, visitors rescued-it's all part of the Meyers service."

Sandy picked up Ricardo's bag. "We'll tell Chief Kane about this," he said. "But I don't suppose there's much he can do about it."

They said good-by then, and Ken and Sandy added their thanks to Ricardo's. Finally they were all crowded in the convertible's front seat, heading back toward the Allen house.

Ken spoke soberly from behind the wheel to the young Mexican beside him.

"You've had a bad introduction to Brentwood," he said. "I just hope we can make it up to you in some way. You'll have to tell us something we can do for you, Ricardo."

"I am most ashamed to say this," Ricardo said quietly, after a moment, "but there is something I will ask you to do for me."

"Good," Sandy said. "Let's hear what it is."

"It is not because of what happened tonight," Ricardo said. "Those men wanted to steal money from someone, I think, and they chose me. They did not know they made a very bad choice. Because I have no money. And that is why I must ask you to-to help me. You see, I have lost the money for my ticket to Mexico.

"Lost it?" Sandy echoed. "When?"

"It was two weeks ago. Robbers took it from my room."

"Tell us about it, Ricardo," Ken said.

They were already within a block of the Allen house. Ken swung around a corner, purposely detouring to give Ricardo the chance to finish his story uninterrupted.

"I was living in a room over a garage," Ricardo said. "It belongs to a very kind family who let me live in it for very little money. On this night I speak of I came home late from the library. I opened the door, and I saw quickly that robbers have been in my room. I do not have many things, but all are on the floor-books, clothes, the letters from my mother-everything."

"And your money was gone?" Ken asked.

"Yes. I had just enough for my airplane ticket to Mexico City, and for the bus that will take me from Mexico City to Rio Claro. It was hidden in my suitcase with my letters. The letters I found on the floor. The money I did not find. I looked everywhere, but it was gone."

"You certainly have been having a run of mighty bad luck, Ricardo," Sandy said. "Losing every cent you had-“

"Oh, no. Not all," Ricardo said quickly. "I had in my pocket that night five dollars. That money the robbers did not get. And at the end of school I received twelve more dollars-the money I had given as a deposit to my laboratory teacher at the beginning of the school year."

"So you've been living for two weeks on seventeen dollars?" Ken asked.

"I did not use it all," Ricardo explained. "I had enough left this morning to pay for my bus ticket to New York."

"And your bus ticket out here, too?"

"For that-" Ricardo hesitated. Then he took a deep breath. "Yes, I must tell you this, too. You see, I have a silver-" He groped for the right word. "It is a round, silver thing on a chain. In Spanish we say amuleto."

"Amulet?" Ken suggested. "A sort of a charm?"

"Yes, amulet, I think," Ricardo said. "It is heavy silver. I wear it always around my neck. So in New York City I take it to a-a pawnshop. The man gave me for it seven dollars. And with this I bought my ticket to Brentwood. But now, you see, I have nothing. And that is why I must ask your help. I must ask to borrow from you enough money to get home to Mexico."

"And enough more to redeem your amulet," Ken reminded him. He dropped one hand from the wheel long enough to touch the young Mexican's arm. "Don't worry, Ricardo. The money is yours-as much as you need. I'm just sorry you didn't tell us when you wrote. We could have sent you some money right away."

"I thought it would be easier to tell you like this," Ricardo said quietly. "You see, I am very much ashamed. I thought when I came to the United States that I would not trouble you. You do not know me. You are friends only of Roberto, not of me. And so I did not write you then, as Roberto asked me to do. But then I found myself in deep trouble, and I did not know what to do. And so I wrote to you. I am most ashamed," he repeated, "that I come to you only like this, when I need help."

Ken smiled at him. "Suppose we were in trouble in Mexico, and came to you for help because you were Roberto's friend. Wouldn't you think we had a right to do that?"

"But of course!" Ricardo said. "Roberto's friends would be my friends, always."

"Well," Sandy said gruffly, "that's the way we feel about it too."

"I know that now," Ricardo said softly. "But before, I thought the United States may be different from Mexico."

"Not that different," Sandy assured him.

"Not in the Allen family, anyway," Ken added. "Someday I'll tell you, Ricardo, what this family has done for me. Then you'll see they're old hands at being good friends."

"I think you also are a good friend," Ricardo said. "But please, there is one more thing I must say, before I can let you do this for me. My mother is a cook. She earns very little. And I do not know how much money I can earn now, when I start to work. So it may be a long time-perhaps one year-before I can send money back to you."

"That's another thing you don't have to worry about," Ken assured him. "In fact, we'll have the whole way to Mexico to discuss the subject. Sandy and I are getting ready to leave for there ourselves in a few days, you know. I don't see why we shouldn't all travel together."

"That's a great idea!” Sandy said. "Then if there's some Spanish word on a menu that confuses me, Ricardo can help out. And speaking of menus-" He broke off and glanced meaningfully past Ricardo to Ken.

"Yes, we'd better get you home to dinner right now," Ken told Ricardo. He knew Sandy understood that he had been driving aimlessly around in order to give Ricardo a chance to talk. "We'll be there in just a minute now."

It was almost two hours later when Mom said, "Ricardo, there's only one piece of this pie left. You can eat it, can't you?"

"I am unable to swallow one more mouthful," Ricardo assured her regretfully. "I think my mother will not believe me when I tell her how much food I ate in this house, at one meal."

"Hmm!" Mom said. "You didn't impress me one bit. Why, compared to Sandy here, you scarcely ate a thing."

"But he is so big!" Ricardo said. "He needs more food than I do."

"You see, Mom?" Sandy said. "Really intelligent people, like Ricardo, understand these things." Silently he handed her his own plate. "Just to save you the trouble of putting it in the refrigerator," he explained, eying the pie.

"Sandy has a motto," Ken told Ricardo, as Mom resignedly transferred the piece of pie to Sandy's plate. "It goes like this: Never put off for tomorrow what you can eat today."

Ricardo joined in the laughter. He was no longer the strained, apologetic boy who had sat between Ken and Sandy on the way to the house. He had relaxed in the warm atmosphere of the Allen home. Ken had convinced him that it was unnecessary to explain his predicament before dinner, as Ricardo had wanted to do. Ken also knew Ricardo would go on feeling as if he were sailing under false colors until all the Allens had been told that he was in need of help.

"Now that we have satisfied the inner man," Pop was saying, "let's have the details of what happened tonight. You know," he told Ricardo, "we don't usually welcome strangers to Brentwood by attacking them."

"What happened on the highway was nothing," Ricardo assured him. "But there is something else I must explain." He looked at Ken. "Now is the time, no?"

"Sure," Ken said. "If you think Ricardo had bad luck in Brentwood," he told the others, "wait until you hear what happened to him a couple of weeks ago."

The Allen family reacted to Ricardo's story just as Ken and Sandy had. Mom plied him with questions to make sure he had had enough to eat during the past two weeks. Pop sputtered his anger, and said that perhaps some editorials should be written, demanding more safeguards for foreign visitors.

Mom had Ricardo's coat in her lap, by then, under the lamp, and was neatly mending the ragged tear.

"I've been thinking," she announced. "Have you had much chance to explore New York since you've been up north here, Ricardo?"

"No," Ricardo told her. "I was there only today, and for only a few hours. And I was very busy"-he was able to smile about it now-"seeking a place that would give me money for my amulet."

"Then what I think," Mom said, "is that you and the boys should spend the next couple of days in the city, seeing the sights. Your father's not in New York, Ken-you can all use his apartment."

"That's a wonderful idea!" Ken said.

"It would be most wonderful," Ricardo agreed. "But, you see, I must leave for Mexico as soon as possible. For each day I stay here, I must borrow more money from you. And as I have explained, it is not possible to know when I can pay back what I will owe."

"Each day you spend in New York will cost you exactly nothing-and that is a final statement, not open to argument," Pop said. "After you've all had a good spree, you can take off for Mexico together."

"He's right, Ricardo," Mom said, nodding at the young Mexican over her sewing. "You will be our guest for your last few days in this country."

"But, please, I could not-" Ricardo began.

"Yes, you can," Mom said firmly. "And now I think you need a good night's sleep. The boys will show you to your room-and they will bring your shirt down here to me, so that I can sew that button on. Go on, all of you-upstairs!"

Ken and Sandy got to their feet.

"Come on, Ricardo," Ken said. "You might as well learn it right now, the way I had to the first night I came here. Pop and Bert and Sandy are big, all right." He grinned upward at his redheaded friend, who topped his own height by six inches. "But around this house it's Mom who's the boss. Tomorrow we'll go to New York, get our plane tickets lined up, and then we'll see the sights for a couple of days. And right now you're going to bed, and you will hand over your shirt when you take it off. Mom has spoken and there's just one thing to do: obey."

Ricardo looked at all of them, his eyes bright. "Roberto said I would find good friends here," he said softly. "But I think even Roberto did not know how good."

CHAPTER III

NOCTURNAL VISITORS

An hour later Ken and Sandy were undressing in their own room. They had helped clear up the dinner dishes, and discussed with Pop the few assignments they would be leaving undone by taking off on their vacation a few days earlier than they had expected.

"I forgot to apologize to you," Sandy muttered, as he bent down to untie his shoelaces.

"Apologize? What for?" Ken asked suspiciously.

"You had a hunch Ricardo might be in trouble when he wrote. I said his only trouble was with his English. I was wrong. You were right. And that happens so seldom," Sandy added, "that I thought you deserved to hear my manly admission of the fact."

Ken grinned briefly. "Well, I've got another hunch right now. See what you think of this one. I've got a hunch there's something peculiar about a poor student, like Ricardo, being the target of two robbery attempts in two weeks. And don't tell me it was a coincidence, because you don't trust coincidences any more than I do."

"Huh?" Sandy straightened up and stared at him. "But in this case, what else could it be?"

"I haven't any idea," Ken admitted. "Unless Ricardo possesses something so valuable that people would ransack his room at school for it-and then follow him all the way down here to make another try for it."

"Look, mastermind," Sandy said patiently, "he did have something valuable in his room. He had enough money to pay for a plane ticket to Mexico. So somebody heard about it, and broke into his room and took it. As for this thing tonight-well, the two men in that car might have noticed him standing beside his bag, decided the bag could be worth a couple of dollars, and pulled up alongside him to grab it."

"Which they didn't do," Ken pointed out. "Instead, they attacked Ricardo."

"Maybe they just planned to hold him down-or knock him out-until they could toss the bag into their car and be ready to take off."

"Maybe," Ken admitted.

"And maybe," Sandy said, "you need a good night's sleep too. I hereby withdraw my apology," he added.

Ken grinned. "I guess I can't blame you. My hunch doesn't make much sense, now that I've said it out loud. So I hereby accept your withdrawn apology, in the spirit in which it is withdrawn."

It was close to noon the next day before they left Brentwood. Mom had insisted upon giving them all a big breakfast. Ken and Sandy had to pack the clothes they had planned to take to Mexico. Then, after saying good-by to Mom, they had spent an hour or so at the Brentwood Advance office, where the boys cleared their desks and made a few necessary phone calls. In the meantime, Bert and Pop had explained to Ricardo the workings of a small-town weekly newspaper. And, finally, they had stopped at Joe Meyers' service station, to thank him once more for his rescue of Ricardo, and to fill the gas tank of their car.

Sandy leaned back behind the wheel and sighed. "We're off!" he said. "What's first on our schedule when we get to New York-after we have lunch, that is? Provided we don't stop somewhere and have lunch along the way."

"I suggest we go to the Global office and pick up our plane tickets," Ken said. "When I phoned Granger this morning he said the office had already ordered ours, and that by this afternoon they'd have the dates on them changed to this coming Saturday, and have Ricardo's ready too."

Ricardo smiled. "Americans are most efficient," he said.

"We won't need cash for the tickets," Ken went on. "I told Granger to pay for them out of that nice big bonus he promised us for our last story. And we'll get travelers' checks before we leave for Mexico. But we'll need some cash for the next couple of days," he added. "I got enough for all of us. Ricardo, here's yours." He handed the boy an envelope he took out of his pocket. "Not that we plan to let you spend anything," Ken told him. "But we thought you might want a small cash loan so you could buy some presents to take home, or something. And we know you want to get your amulet back.'

"Yes," Ricardo said. "That I want very much to do. Never before has it been out of my hands-not since my father gave it to me before he died." He looked into the envelope. "But I do not need so much!” he protested.

"Well, you never can tell," Ken said. "Anyway, we can spare it right now. And we can wait more than a year before we get it back."

Ten minutes later Sandy decided that he couldn't drive the whole distance to New York without a sustaining meal. They had a leisurely lunch at a big roadside restaurant, and then drove on without stopping until Sandy parked the car near the pawnshop on Eighth Avenue where Ricardo had left his amulet.

Ken and Sandy went with their new friend into the crowded little shop.

The gray-haired man behind the counter took Ricardo's ticket, studied the number on it, and then reached into a drawer and took out a small envelope. When he upended it over the counter a heavy silver disk fell out.

The disk was about the size of a silver dollar, but thicker. One face was smooth, polished to a soft gloss by years of wear. The other face bore a deeply engraved carving of a coat of arms consisting of a pair of crossed swords and a shield. A thin silver chain ran through the small hole drilled close to the rim.

Ricardo accepted the change from the bill he had given the shop owner. Then he slipped the chain of the amulet over his head and let die disk disappear inside his shirt.

"Now," he said, "I am ready to enjoy the great city of New York."

"And we're ready to show it to you," Sandy assured him. "First we'll give you a look at the office of that great international news service, Global News."

They spent an hour at Global, leaving their car in the garage beneath the building. Steve Granger himself took the time to conduct Ricardo on a tour of the premises, and gave him a souvenir of his visit, a teletyped dispatch from Mexico.

Afterward, Ken and Sandy took Ricardo to the top of the Empire State Building, to look down on the millions of lights that blinked into life as dusk fell over the city. Then they had dinner at a Mexican restaurant, where Ricardo unexpectedly asserted himself and ordered a meal such as the boys had never before enjoyed north of the Rio Grande.

Later, they walked under the blazing lights of Times Square, and ate monumental ice-cream sundaes at a soda fountain, before they retrieved the convertible, parked it in a garage on Sixty-ninth Street, and dragged themselves and their baggage up the three flights of stairs to Richard Holt's seldom-used apartment on Seventieth Street. They were asleep before midnight.

The next morning they were out again by nine o'clock, for a full day of sightseeing that included a boat ride to the Statue of Liberty, another boat ride around the whole island of Manhattan, a tour of Radio City, and a visit to the Museum of Natural History.

Ricardo looked tired as they climbed the broad steps to the museum. But once inside, standing before the reconstructed skeleton of a huge dinosaur, he came suddenly to life.

"Ricardo," Ken said, smiling at him, "you look as if you're more excited by the past than you are by the present."

Ricardo grinned. "It is my secret hope," he confessed, "to become an archaeologist someday. I have studied agriculture, you understand. I have learned how to make good crops come out of the earth. But someday also I hope to dig in the earth for ancient things."

"Remind me," Sandy said, "to buy a good book to read on the plane. Something tells me you two will be talking paleontology and archaeology all the way. Ken's a bug for that stuff too," he told Ricardo.

"It is true?" Ricardo asked eagerly.

"It's true all right," Ken said. "And Sandy and I have visited a couple of really interesting digs. I'll tell you all about them sometime."

"I will remind you-if you forget," Ricardo assured him.

They didn't leave the museum until a guard pointed out to them that the hour of closing had arrived.

"This has been one of the most exciting days of my life," Ricardo announced solemnly.

"And it's not over yet," Sandy assured him. "I will now take over the guiding of this tour, and introduce you to some of the best French food on this side of the Atlantic. You like French food, Ricardo?"

"I do not know," Ricardo said. "I have never eaten any." Then he grinned. "But I have never done any of the things I have done this day and yesterday, and I have been liking them all very much. So I am sure I will also like French food."

Ricardo did like French food. He was also impressed by the attention the boys received from the headwaiter.

"You come here often?" he whispered, after that resplendent gentleman had paused at their table for the third time to make sure they were being well taken care of.

Ken grinned. "We have been here exactly once before. But we were here with my father, who knows almost everyone. We find that makes a difference."

They also received more than their share of attention at the basketball game they attended that evening. The passes Granger had provided gave them seats in the press box, and Ricardo was torn between watching the game and watching the professional sports commentators handle their assignments.

"No one in Rio Claro will believe me when I tell them of this day," Ricardo announced, when they finally emerged into the chilly night air.

"How shall we get uptown to the apartment?" Sandy asked. "Subway, bus, or taxi? It's your choice, Ricardo."

"Subway," Ricardo chose. "That is one New York experience I have not yet enjoyed."

Ken and Sandy stood with him at the forward end of the front car of the train, watching his pleasure at the colored lights that seemed to rush toward them in the dark tunnel.

"No one in Rio Claro will believe," Ricardo repeated, to himself. "No one."

They were emerging from the subway exit when Sandy said, "Wait! I've just realized there isn't a bite to eat in the apartment. Remember-we went out to breakfast this morning? It's not safe to be in a house where there isn't even a quart of milk. Let's go around the block and pick up something at that store that always stays open all night."

"You are hungry-after that big dinner?" Ricardo asked, eyes wide.

"Not right this minute," Sandy admitted. "But how can I answer for the way I may be feeling in a quarter of an hour?"

At the all-night grocery Sandy bought two containers of milk, two different kinds of cookies, and several large red apples.

"Now," he announced, "we can go home. These are meager rations, but they ought to get us through the night."

A few minutes later Ken opened the downstairs vestibule door of the building in which his father had kept an apartment for as long as Ken could remember.

"Don't forget what I told you last night," he said in a low voice. "We make as little noise as possible once we're inside. That old Mr. Taylor in the apartment alongside Dad's raises a terrible row if he's waked up. And he's so used to Dad's place being empty and quiet that he wakes up if we so much as drop a pin."

"I remember," Ricardo whispered.

"Do you think it's all right if we breathe?" Sandy wanted to know.

"Shh!” Ken told him.

They walked on tiptoe up the stairs of the old house, and moved silently past the dark closed door of the Taylor apartment to the door bearing the small card that read Richard Holt.

Ken slid his key into the lock and turned it. As he pushed the door open he reached inside and felt for the light switch on the wall. Then he motioned Ricardo and Sandy into his father's living room, now brightly lighted, and stepped in after them. He closed the door carefully, so that it shut with only the lightest click.

"Milk, anyone?" Sandy fished one of the containers out of the paper bag he carried and held it up temptingly. He was heading for the unlighted kitchen as he spoke, the bag of groceries cradled in his left arm, the container of milk carried like a staff in his right hand.

"How about you, Ricardo?" Ken asked. "Would you-?" He broke off abruptly at the sight of Sandy slowly backing out of the kitchen, step by step. In his amazement Ken forgot to keep his voice lowered. "Sandy!" he said loudly. "What's-?"

Then once more he broke off, and his eyes widened.

Sandy was still backing into the living room, still carrying the grocery bag in one hand, the milk bottle in the other. His body was rigid, his back ramrod straight. He seemed to be staring fixedly at the object that had just become visible to Ken.

It was a small revolver, its size increased by the silencer affixed to its barrel.

The revolver was pointed at Sandy, and was moving as he moved. When it emerged fully into the lighted living room, the boys could see that it was in a black-gloved hand.

The owner of the hand came into view, inch by inch, like a figure photographed in slow motion. Ken saw the black-clothed arm, then the head topped by a black hat with a brim tilted steeply over the face.

The black mask covering the upper part of the face made a grim frame for eyes glittering through two narrow slits.

The voice that spoke suddenly from beneath the mask was a toneless whisper. "No noise!" it commanded. "Back-you! All three of you stand together." A small authoritative gesture of the gun gave emphasis to the words.

CHAPTER IV

HIDDEN SECRET

The man was in full view by the time he spoke-a slim figure dressed in black from head to foot. As he stepped forward into the living room a second figure appeared behind him, also dressed in black and seeming identical to the first except that he had no gun.

"Over there-against the wall!" the man with the gun commanded. "And empty your pockets, all of you. Drop everything in them on the floor." The words were all spoken in a hoarse whisper.

Ken's eye was on the round black hole in the muzzle of the gun. He was scarcely aware of a swift blurred motion, of something white hurtling through the air toward the man holding the gun.

Then it struck the man on the shoulder with a dull thud. Sandy had hurled the milk container in his hand, and it had landed with deadly accuracy. White liquid exploded into the air, splashing across the man's face, spurting upward toward the ceiling, cascading down toward the floor.

The man staggered backward with a strangled shout. His twisting body caromed against a table. His flailing arm struck a glass decanter surrounded by a circle of glasses, and sent them flying. The glassware shattered on a strip of bare floor with a deafening crash.

Ken started toward the milk-spattered figure. So did Sandy. But the man was too fast for them. The gun in his hand steadied even before he regained his balance. And even as he pointed it straight at Sandy's head, his companion whipped out a second revolver and turned it on Ken. It moved just enough, left and right in a tiny arc, to cover Ricardo too.

While he dashed milk from the lower part of his face with a drenched sleeve, the man who had already spoken, spoke again. "This is the last time I'll tell you," he said, still in that same hoarse whisper. "The next time I'll let the gun do my talking for me. And don't think I won't enjoy it! Line up over against the wall. And empty your pockets. Quick!"

Ken had taken one backward step in response to the command when the room suddenly resounded to the noise of loud thumps against the wall, and an angry voice shouting, "Can't you let a man sleep?"

The voice was coming from the other apartment on the floor. The intervening wall muffled it slightly, but the words were clear enough. So was the fury behind them.

"You hear me in there?" the voice shouted again.

The two masked men exchanged a swift, alarmed glance.

The milk-spattered gunman gestured with his weapon. "Go on-you! Up against the wall!"

"So you're ashamed to answer me, are you?" The shout through the wall was louder than ever. "Well, I've had enough. I'm coming in there and see for myself what's going on!"

The two armed men stood motionless.

Then the one who had kept silent made a dash for the door. "I'm leaving!" he said over his shoulder.

The other turned toward him, looked swiftly back at the boys, then turned toward the door again. His companion had already flung it open and was clattering down the hall toward the stairs. The noise he was making apparently settled the remaining burglar's confusion. Suddenly he, too, was at the door.

He had moved toward it sideways, keeping his gun trained on the boys. Then in a single lightning-like movement he was across the threshold and slamming the door shut with a crash.

For an instant Ken remained rigid where he stood, listening as if paralyzed to the sound of two pairs of feet pounding down the stairs.

Then he leaped toward the door. In the same instant, Sandy yelled, "Police! I'll call the police!" and dropped the bag of groceries with a thud as he stumbled over a chair on the way to the telephone.

The doorknob was slippery under Ken's wet palm. Sandy was dialing furiously before Ken turned the knob successfully and jerked the door open.

The outraged figure in a woolen bathrobe, on the other side of the door, had a fist raised ready to deliver a knock. The fist stayed in the air, only inches from Ken's face.

"Police!" Richard Holt's furious neighbor echoed Sandy's word in a voice that squeaked with anger. The fringe of hair around his bald crown stood up in spikes. His thin cheeks quivered. "I'll call the police! And I'll tell them all about the wild party you're having in here!"

The slamming of the vestibule door three flights below was like an exclamation point at the end of the threatening statement.

Ken let out his breath and stepped back away from the door. "Come in, Mr. Taylor. I can't tell you how glad we are to see you. Hold it, Sandy," he said over his shoulder. "Those men are out of the house already. They'll be clear of the neighborhood before a squad car could get here. Please, Mr. Taylor-come in," he repeated.

On stiff legs, in candy-striped pajamas, the man crossed the threshold. "What are you trying to do?" he demanded. "Confuse me? What's this about men being clear of the neighborhood-and you being glad to see me?"

"It's true, Mr. Taylor," Ken assured him. "I don't suppose we were ever more glad to see anybody in our lives."

"That's right, sir." Sandy spoke up from the other side of the room. Cookie boxes lay at his feet. Broken glass lay everywhere, in puddles of spilled milk.

"You young men are a disgrace!" Taylor snapped. "And I'm going to make sure your father hears about this!"

"We'll tell him ourselves," Ken said quickly. "And we'll tell him how grateful we are to you for scaring off those two burglars, by pounding on the wall.'

"Burglars?" Taylor snapped suspiciously. "What land of a cock-and-bull story are you trying to tell me?"

"It's true, sir," Sandy said. "You probably heard them running down the stairs as you came along the hall."

"Certainly I heard some of your rowdy friends trying to get away before I could call the authorities!" Taylor said. "Don't think you're fooling me, Kenneth Holt," he went on, shaking his finger in Ken's face.

With an effort Ken kept his face straight. "We're very sorry you were waked up, Mr. Taylor. Honestly we are. Even if you did perhaps save our lives-not to mention all the cash we happen to be carrying."

"So you're sorry, are you?" The man ignored the rest of Ken's words, as if he refused to listen to anything he didn't understand. "Well, in that case I may let you off this time. I say I may-if I don't hear another sound out of this apartment tonight. Now we'll just see if you can behave yourselves!" He glared at them once more, sniffed, and then turned on his slippered heels and marched toward the door.

Holding on to the doorknob, he faced them briefly once more, his eye on Ken. "I might add that I am surprised that the son of that fine writer, Richard Holt, could invent no more plausible story than yours to account for the unmistakable noise of young men making fools of themselves when they should be in bed." An instant later the door clicked firmly shut behind his thin, erect back.

"Wow!" Sandy said softly. "Even that fine writer, Richard Holt," he said, in a stifled whisper, "couldn't invent a marathon sentence like that last one."

"But it was most fortunate that he came here- was it not?" Ricardo said.

Ken and Sandy sobered abruptly, their brief mood of hysterical amusement gone in an instant.

"It was indeed," Sandy said feelingly. "And I do think we ought to call the police, anyway, Ken. We ought to report those two thugs, even if they didn't get anything."

"Come to think of it, we're not sure they didn't," Ken said. “I’ll take a look around and see if any-thing's missing, while you phone the police."

"I'll ask them to come in quietly," Sandy said, reaching for the phone.

"Let's go check over our stuff in the bedrooms, Ricardo," Ken said. He put an arm over the young Mexican's slender shoulders. "You'll probably never believe this, Ricardo, but most of the time this is really a pretty law-abiding country."

Ricardo answered him earnestly. "You do not have to tell me this. I know. It is only a coincidence that has brought me three times in lie path of men who do not abide by the law."

Ken glanced at him. "Yes," he said thoughtfully. "A coincidence."

Within ten minutes two plain-clothes men were in the apartment, notebooks in hand, questions ready. Sandy had gone downstairs to let them in, to avoid the sound of the bell, and they were cheerfully cooperating to maintain the quiet he had asked for.

"It's lucky for you that you live next door to a light sleeper," one of them said. "Though, so far as we're concerned, we wish your masked visitors hadn't taken off in such a hurry. We'd have been glad to get our hands on them. There's been quite a rash of burglaries in this part of town lately, and your two may be responsible for the lot of them. You say nothing is missing?" he added.

"That's right-so far as we can tell," Ken told him. "The stuff in our bags is tumbled around, but it all seems to be there. Sandy's camera equipment is safe, and that's probably among the most valuable stuff in the apartment."

"Hmm. Sounds as if they weren't interested in anything but cash. And, as you tell the story, they didn't have time to get yours before your neighbor started yelling."

There were more questions about the two housebreakers themselves, but the boys could only describe their height as medium and their build as fairly slender.

One of the plain-clothes men returned to the living room after a second inspection of the fire-escape window through which the unsuccessful burglars had forced an entrance. "If these are the men we've been hoping to round up, we may have some luck pretty soon," he said. "They're getting careless. They didn t seem to care how much they marked up that lock, in order to force it open. We'll let you know if we do pick them up," he added.

"Thanks," Ken said. "But we won't be here after Saturday night. You could leave word at Global News, though."

"Right," the man said. "If there's any word to leave, that is. Don't forget to put a new lock on that window," he reminded Ken, as they prepared to leave. "First time I've ever heard of a milk container being used as a weapon," he added musingly.

"I don't recommend it," Sandy admitted. "Not if you toss it in a place you're going to have to clean up yourself.

"I'm sorry about the milk, Ken," Sandy said, when the detectives had gone. "But it seemed like a good idea at the time."

"It was," Ken assured him. "If I'd just been a little faster I might have grabbed that gun while he was off balance." He shook his head. "Oh, well- we haven't lost anything. I guess we were lucky. And this job won't take long if we get right at it. But you ought to go to bed, Ricardo," he added. "It's been quite a day!"

"Sure," Sandy urged. "Go on, Ricardo. We're just sorry we walked you into this performance by the New York underworld."

"Oh, no," Ricardo said. "I wish to help. I am not tired. Looking into a gun barrel wakes one up-no?"

Ken grinned briefly. "It does, at that," he agreed. "All right. Let's get started then."

Nearly an hour went by before they were satisfied that they had scrubbed the milk out of Richard Holt's rug and off his walls. Then, utterly exhausted, they slumped down around the little kitchen table, to drink the remaining quart of milk and eat some of Sandy's cookies.

Their sleeves were rolled up, their ties off, their shirts open. When Ricardo leaned across the table to take the glass Sandy had filled for him, his silver amulet swung out and banged against the wood.

Ricardo caught it up quickly, with an alarmed glance in the direction of the Taylor apartment.

"Don't worry," Ken told him, grinning wearily. "We're pretty safe out here, with the kitchen door shut." Then he added abruptly, "Ricardo, is that thing valuable-your amulet?"

"Ken!" Sandy stared at him. "It's a good thing Mom isn't around to hear you asking a rude question like that." He spoke the next words in an imitation of his mother's voice when she was shocked or horrified. "Ken, I'm surprised at you!"

Tm sorry, Ricardo," Ken said. "But-"

"I do not mind the question," Ricardo said, smiling. "To such good friends I would tell anything." He looked down at the heavy disk in his hand. "But all I can tell you of this is that it is worth seven dollars- because that is what the man in the pawnshop gave me for it."

"Sorry," Ken said. "I just meant-well, I assume it's a family heirloom-you know, handed down from one generation to the next."

"No," Ricardo said. "It is true my father handed it to me, and his father handed it to him. But it does not belong to our family."

"Huh?" Now it was Sandy who stared in open curiosity. "But if it's been in your family for three generations, then-well, then who does it belong to, if not to you?"

"I do not know," Ricardo said. "It is very simple," he went on. "My grandfather told my father to keep it until someone asked him for it. Only the real owner, he said, would ask for it, because only the real owner would know that our family-the Montez family-was keeping it for him. My father told me the same thing. So it is not mine, you see. I only keep it until someone asks for it."

"And you'll just hand it over-like that-to anyone who asks?" Ken's puzzlement sounded clearly in his voice.

"First he will tell me what is written on the silver," Ricardo explained. "Then I will know he is the person to whom I should give it." He slipped it over his head and handed Ken the amulet. "You can see the writing-there-but it is so small you can read it only through a magnifying glass."

"Mind if we look?" Sandy asked. "Ken's father's got a good glass." He started to push back his chair.

Ken stopped him with a hand on his arm. "Now who's prying?" he demanded. Then he went on, "Just a minute, Sandy. Even if Ricardo doesn't mind our looking at it, I've got a question I want to ask first. Is there any chance, Ricardo, that this amulet is so valuable that somebody has been trying to steal it- trying on three different occasions?"

"Oh, Ken!" Sandy clapped a hand to his brow. "Not again! We're not going to have that crazy hunch of yours following us all over Mexico?"

"Let Ricardo answer the question-if he doesn't mind," Ken said quietly.

Ricardo looked at Ken steadily. It was clear that he was thinking back over the theft that had taken place while he was in school, the attack on him in Brent-wood, and the attempted burglary that had just occurred in Richard Holt's apartment.

"I do not think it is true, Ken," he said, shaking his head. "You see, only a man who has the right to this amulet would even know it exists, and would know that my family is keeping it. And such a man would know about the writing, I think. And so he could tell me about the writing, and ask me for the amulet- and I would give it to him gladly. I do not wish to keep it. I keep it only because it is my duty."

"Yes," Ken said. "I see."

"You're sure you do?" Sandy muttered.

"And you haven't any idea who might someday come to you and claim the amulet?" Ken asked. "If he was a friend of your grandfather's, he'll probably be pretty old now."

"I do not really know-no," Ricardo said. "But I think it will be somebody who is of a family called Obregon, or who is perhaps a friend of that family. I think this because the writing here"-he pointed to the minuscule engraving-"says de la casa Obregon, which means 'of the house of Obregon.' I think it also because my grandfather worked for such a family many years ago."

"Do you know anybody by that name?" Ken asked.

"Oh, no," Ricardo said. "I think they live a long way from Rio Claro," he explained. "I think they live close to the border of Guatemala, near the town of San Cristobal de las Casas."

"What makes you think that?" Sandy wanted to know.

"Did you ever try to get in touch with them?" Ken asked in the same moment.

Ricardo shook his head at Ken. "My grandfather did not tell us to do that," he said. "He said only that we should keep the amulet. And when I speak of San Cristobal de las Casas, it is because I think my father told me that my grandfather lived near that town."

He looked over at the amulet that Ken was holding in his hand and fingering curiously.

"I am sorry that I do not know more," Ricardo said. "To me the amulet was never of much interest, because I have had it almost all my life. When I do not wear it, I have a strange feeling, but that is only because I have worn it for many years. It is like-how should I say it?-like my skin. It is hard to remember what my father told me, but I think I remember that the house of Obregon was a big hacienda and the family owned much land." He smiled suddenly. "But perhaps he was making only a good story for a small boy."

"Am I seeing things?" Ken asked suddenly. "Or is there an almost invisible line around the edge of this disk? Does this thing split open into two halves, Ricardo?"

"Split open?" Ricardo repeated wonderingly, and took the disk from Ken's outstretched hand. "It is solid silver, I think. But-" His voice trailed off as he held the disk closer to the light, peering intently at the edge.

"I'm going to get that magnifying glass of your father's," Sandy muttered, and left his place at the table. He was back a moment later. "Here, Ricardo," he said. "Look at it with this."

Ricardo studied the disk for another long moment. "You look," he said then, handing it to Sandy.

"You know," Sandy said a moment later, "I think this is really two disks fastened together. Here." He gave it to Ken.

"I'm sure of it," Ken said, after a careful inspection.

His eyes met Sandy's. They were both fascinated by the trinket that Ricardo had worn so casually nearly all his life. Their weariness of a few moments earlier had been completely forgotten.

"I don't suppose you'd like to try to open it?" Sandy asked their guest tentatively.

But Ricardo too was fascinated, caught up in their contagious curiosity. "You think it could be opened -and without breaking it?" he asked. "That would be exciting, no?"

"It sure would be," Sandy agreed. "Who knows what we might find in here? I think I could promise not to break it, Ricardo, if you'll let me try. I'll be very careful."

"He's good at this sort of thing," Ken assured Ricardo.

"Please, yes. I wish you would try," Ricardo said.

Eagerly they rearranged the chairs so that Sandy's was directly under the brightest light in the kitchen.

'Til hold the magnifying glass for you," Ken offered.

Sandy was opening up the smallest blade of his penknife-a thin razor-edged sliver of hard steel.

"All right," he said. He moved the silver disk into position under the light. "That's it. Keep the glass right there."

Three pairs of eyes watched his blade, as it probed gently at that nearly invisible line around the rim.

The minutes ticked by, long slow minutes. Ken knew his hand would soon begin to tremble, and that any movement of the glass would hinder Sandy's job.

And then it happened. The point of the knife disappeared. The faintest of clicks sounded in the silence of the room.

Very carefully, very slowly, Sandy twisted the knife.

Another faint click sounded, followed by a tiny snap.

And before their staring eyes the amulet split into two halves, both still dangling from the silver chain that passed through the two matching holes.

"Mira! Ricardo lapsed into Spanish in his excitement. "Look!" he repeated in English. "There is a piece of paper in this half!" His slim brown finger barely touched one of the two hollowed-out disks that Sandy laid gently on the table. He was no less excited than Ken and Sandy, no less eager to learn whatever secret the tiny bit of folded paper might contain.

"If we used tweezers," Ken said, "I think we could get it out safely. Wait!"

He was back in the kitchen in less than a minute. "Here, Ricardo," he said. "You'd better do it yourself."

Ricardo took the tiny instrument in his right hand, steadied that hand with his left, and slowly lifted the paper out of the shallow recess where it had lain concealed for decades.

"It is folded many times!" Ricardo breathed. "Sandy, you open it!”

Sandy used tweezers and knife blade and patience.

Once, twice, three times he unfolded the paper, and then three times more, until what had been a square less than an inch across measured some eight inches to a side.

It was a fragile bit of tissue-thin stuff, faintly yellowed. And on it, in thin black lines, had been drawn a curious design.

Ricardo caught his breath. "Look!” he whispered. He was pointing to a spot in the middle of the design. "The word written there is tesoro. It means treasure. This must be a treasure map!"

CHAPTER V

BURIED TREASURE

All three of them stared as if hypnotized at the flimsy bit of paper.

"I'd sure like to believe you, Ricardo," Sandy said finally. "But it doesn't look much like a map to me. It looks more like-well-maybe a diagram for a piece of laboratory equipment. Those straight lines and angles don't look like roads."

"But there's an arrow on this side marked N, for north-the kind of arrow you do find on maps," Ken said. Carefully he turned the paper until the arrow pointed upward-away from the three figures bending over the table. "Those double lines don't look like roads, though," he admitted. "They seem to make three capital letters, joined together-KEX, but with a curve on top of the K's upright. But wait! There are some more words! Here's one-and there's another!"

They all bent closer. The words were written in tiny delicate letters, but each letter had been drawn with such care that they could be read without magnification.

"This is entrada-entrance," Ricardo said, pointing to the printed word at the upper-right corner of the X. "And the word right below it, inside those lines, is escalera-stairs," he went on breathlessly. "And there, at the other end"-his finger touched the bottom of the K's upright-"are the words salida peligrosa. They mean exit and dangerous-a dangerous exit!"

"You know," Ken said suddenly, "these lines might indicate passageways in a garden maze! Or no-wait! That word escalera-stairway. If there's a stairway close to the entrada-the entrance-this must be the drawing of passageways on the upper floor of something, or of-of underground passages!"

"That must be it! They're underground passages," Sandy said excitedly, "reached by a stairway. And at the heart of the crisscrossed passages is some sort of treasure."

"There are still more words," Ricardo showed them. "Look-this one says manatial. That means a spring-a spring of water. And these words here, techo bajo, mean low roof. Both those things one could find underground, no?"

"Sure!" Sandy agreed. "And what's this squiggle of lines here, Ricardo, with the letter S beside it?"

Ricardo looked at the spot Sandy indicated, at the end of the curved tip of the K's upright. Then he picked up the magnifying glass and looked at it again.

"It is a snake-a serpent," he said finally, "with feathers around its head! The drawing is very tiny, but I think I am right because the S could stand for serpiente-serpent."

"A plumed serpent?" Ken asked eagerly. "Could that be it?"

"Whoever heard of a plumed serpent?" Sandy demanded.

"Ricardo has," Ken assured him.

"One of the gods of the Toltecs, an ancient tribe of Mexico, was a plumed serpent," Ricardo said. He looked at Ken out of eyes blazing with excitement. "Do you think there might be here a stone carving of the plumed serpent-one which archaeologists have never yet found, perhaps?"

Ken looked back at him, equally excited. "What a find it would be!" he said.

"Listen, you intrepid archaeologists," Sandy said, "the important thing on this little piece of paper is the word tesoro. And there are two more things on it you haven't noticed yet-two things that practically tell us where the treasure is. Look, here on the edge of the paper. It says La Hacienda Obregon-the Obregon hacienda. Right, Ricardo?"

Ricardo nodded dazedly.

"And I can translate this too," Sandy went on. "Escala must mean scale, and it therefore says scale: 1 to 500. In other words we have here a map, drawn to scale, showing us exactly where a treasure has been hidden at tie Obregon hacienda! And Ricardo was saying just a little while ago that the Obregons lived at-what was the name of the town?"

"San Cristobal de las Casas," Ricardo repeated. "But I said only that I thought they lived there."

"It's good enough to go on," Sandy assured him. "We could check up and find out. The information must be available somewhere. And we'll get whatever kind of permission is necessary-and we'll spend our vacation treasure hunting! Wow!"

He clapped a hand over his mouth to stifle the final shout, and then added in a whisper, "Well, what do you think? Isn't it a terrific idea?"

"It's a terrific idea to go hunting for a plumed serpent," Ken said. "But don't forget this map doesn't belong to you and me."

Ricardo's face sobered. "I had almost forgotten. It does not belong to me, either. I am only holding it in trust for-for whoever will ask for it someday."

"But, Ricardo," Sandy protested, "your family's been holding this thing for three generations! Maybe nobody's ever going to claim it. Besides," he went on swiftly, "we wouldn't keep the treasure anyway, if we ever did find it. It could go right into a vault and stay there until it's claimed. But imagine the excitement of looking for it! Why, it's the kind of thing you dream of!"

Ricardo didn't answer for a long moment. "I think perhaps it would not really be a wrong thing to do -to try to use this map," he said finally. "If we should truly discover an ancient statue of a plumed serpent-then it would be the property of the government of Mexico. That is the law. I know. And if there is a treasure of gold or silver here, then I think it would be the property of the Obregon family. But there are so many questions in my mind now. Where is the Obregon family? Why has no one ever come to claim this amulet in so many years? And also, of course"-he sent them a small flashing smile- "there is the question of how I, who have no money, could go on an expedition for hunting treasure. Yet I think it is necessary for the honor of my family that I should take part in such an expedition. Even to my good friends I could not give this map we have kept for so long."

"Of course you couldn't," Ken said firmly. "We wouldn't go without you, anyway. But that last question of yours is no question at all, Ricardo. You'd go as our guest. This is our vacation and we've saved up for it. Besides, if we really did find something, Global News might pay us such a whacking fee for the story that we'd wind up with more money than we're starting with. So just forget that part of it. If we go, you go too-and the expenses are our affair."

"Right," Sandy said firmly. "And I've just had an idea about how we might get the answer to another of your questions, Ricardo. You want to know about the Obregons. We'll all have to know something about them, if we hope to get permission to do any prowling around on their property. And Ramon is the man who can find out all there is to know."

"Of course!" Ken grinned at him. "Let's call him right now!"

"Ramon?" Ricardo repeated questioningly.

"Captain Ramon Arturo Fernandez Gonzalez," Sandy explained, giving the long roll of syllables his best Spanish accent.

Quickly he and Ken explained how they had come to know the Mexican police officer during their first visit to Mexico, and how they had cemented their relationship with more recent encounters.

"His heart's as big as his name is long," Sandy concluded. "All we have to do is ask him to give us a quick rundown on the Obregons-where they live now, so that we can get in touch with them, and where they lived when your grandfather was alive.

"Of course," he added thoughtfully, "we may find out there's nothing for us to be excited about at all. Maybe your grandfather was given just one of several copies of this map, Ricardo-just as an extra form of insurance for the family. And, if that's the case, the Obregons may have removed their treasure long ago. At least that would explain why nobody ever claimed the amulet."

"I have one other question," Ricardo said hesitantly. "Perhaps you have seen something on this map that I do not see," he went on. "But to me it does not give all the information we would need, if we wished to use it."

"What's left out?" Sandy wanted to know. "It tells us about the Obregon hacienda-and we can find out where that is." He stopped abruptly and his jaw dropped.

"Of course!" he said then. "We don't have any- what do they call it?-any frame of reference! If these are underground tunnels, and the entrance is in plain sight-well, then I suppose anyone could find it. But then there'd be no point in a secret map, because anyone could follow the tunnels once they'd got inside them. And probably somebody did, long ago. But if the entrance isn't in plain sight-then how are we going to find it?"

"That was my question," Ricardo admitted unhappily. "You see, a hacienda, especially in the old days, could cover many, many thousands of acres. So it does not help us much only to know that these tunnels are somewhere on a hacienda. If it is necessary to dig in the earth to find them, we might dig for years and never-"

Ken had been studying the map as Sandy and Ricardo spoke. Now he interrupted Ricardo with a sudden "Look! This may be the clue. The drawing on this sheet of paper covers only about a three-inch square in the middle. There s a lot of blank space around it. And there must have been a reason why they used such a big sheet of paper, especially since they were going to fold it up into that silver disk. So maybe the sheet of paper represents the whole hacienda, and-" He stopped when he saw Sandy shaking his head.

"I just did some rough arithmetic," Sandy said. "At the scale of that map-five hundred to one-that whole sheet of paper represents a square of less than four hundred feet to a side. No self-respecting hacienda could be that small."

"Oh," Ken said.

They were all silent for a moment.

Then Sandy bent closer over the paper and said suddenly, "But how about this? Suppose the paper represents the hacienda's walled enclosure. Wouldn't there be such a thing, Ricardo?"

"Many hacienda owners built walls around their homes and other buildings," Ricardo agreed. "A family's house would be inside the wall, and perhaps the stables and many other buildings-often a small chapel, and even a school if there were many children belonging to the hacienda."

"Ah-ha!" Sandy said. "And take a look at these." He pointed in turn to four small dots, each one just inside a corner of the paper. "These dots might represent the four corners of a square enclosure- or even the towers at the corners, if the walls had towers."

"You've hit it, Sandy!" Ken said enthusiastically. "And now all well need will be a ruler, and a compass maybe, in order to figure out just where to start digging. I'll go phone Ramon now, and-" He took a deep breath and then continued more slowly. "You don't think we're going too fast?" he asked.

"You're sure it's all right with you, Ricardo?"

"It is all right," Ricardo said quietly. "I think the Montez family will not be failing its responsibility if it tries at last to learn something of this mysterious paper placed in our hands so long ago."

The long-distance telephone call was put through swiftly. To Ken's relief, the man at the other end of the line, in Mexico City, said that Captain Gonzalez was then in the office.

A moment later the familiar, heavily accented voice was saying, "Ken Holtl That is you? Are you here? In Mexico?"

"No, in New York, Ramon," Ken told him.

"And you call me from so far? You are in trouble?" Gonzalez asked.

"No. Nothing like that. We just need a little help and advice. Its like this." As rapidly as he could, Ken explained about Ricardo and his amulet and the map they had just discovered inside it.

"We were planning a vacation in Mexico, anyway," he concluded, "and so we thought we'd like to do a little treasure hunting-"

"Treasure hunting!" Gonzalez repeated the words scornfully. "If all the people who have come to Mexico with treasure maps were laid one after the other, they would reach from Yucatan to Guadalajara! You are too intelligent to fall for that old game! If you need exercise, and you like to dig, you may dig in my garden," Gonzalez went on. Then suddenly he relented. "Bueno, amigo. You have been good friends to me. Now you call me to get information, no? . . . Very well. Tell me what you wish to know. I will get you the information if it is available."

"Thanks, Ramon," Ken said gratefully. "Well, what we want to know is this . . ."

"Yes, yes . . ." Gonzalez was murmuring a moment later. "The Obregon family . . . yes, I understand. Bueno, amigo. I will make inquiries. I will telephone you when I have learned something of interest."

"Great!" Ken said. "Thanks-and make that call collect."

He rang off. Sandy and Ricardo were standing beside him. Ken had turned the receiver slightly away from his ear, and he knew that they had also heard Ramon's promise.

"He won't be able to phone back for at least a couple of hours," Ken said. "Let's get some sleep."

When the telephone extension beside Ken's bed woke him some time later, he instinctively looked at the window as he grabbed the receiver. He was relieved to see that it was broad daylight. The bantamlike Mr. Taylor couldn't complain that the bell had waked him in the middle of the night.

"Yes?" Ken said. "Ken Holt here." A moment later he sat bolt upright. "Yes," he told the operator. “I’ll accept a collect call from Mexico City!"

He covered the receiver with his hand. "Sandy!" he said sharply. "Wake up! Get Ricardo too! Ramon's calling back."

Sandy was dragging a stumbling Ricardo into the room as Gonzales' voice came over the wire. Ken tilted the receiver so that it would be audible to all three of them.

"Ken," the police captain said, "the old Obregon hacienda is just where you thought-right outside the town of San Cristobal de las Casas. A most interesting town, amigo. The various Indian tribes in the surrounding mountains still preserve many old ways of life."

"I'm glad to hear it," Ken assured him. "I'm sure we'll find the town fascinating. But right now-"

"Yes, yes, I understand," Gonzalez interrupted, and Ken could sense the man's amusement over the thousands of miles of telephone line. "Right now you wish to know if you can play at treasure hunting. Very well. I will tell you what I have learned. Since the 1910 revolution, the hacienda property has become part of a state forest preserve. The old enclosure where the house and outbuildings once stood is now in ruins. Therefore I have been informed that you can do no harm if you dig about in there. And I am obtaining for you the necessary papers of permission from the government office in charge of such things."

"That's great!" Ken said.

"And this map you speak of," Gonzalez went on. "Perhaps it is not a fake after all. A man named Montez was the accountant for the Obregon family -the sort of man they might trust with knowledge of a family treasure if they feared the coming of the peons' army."

"That's good news too," Ken said. "But what about the Obregons themselves? Won't we have to ask their permission to-?"

"No, amigo. That will not be necessary," Gonzalez told him. "Of course anything you find should be reported to the federal government. I have already given my word that you will do that. But the Obregons, no-there is no problem there. The entire family was wiped out during the revolution, at the same time the hacienda was destroyed.

"Believe me, Ken," Gonzalez added, "I feel sure you would do better to spend your vacation studying the Indian villages of that most interesting region. But I understand how young you are-you and your redheaded friend-and how foolish. So go and search for your treasure. No one will try to prevent you-except perhaps a greedy ghost!"

CHAPTER VI

WILD-GOOSE CHASE

The next forty-eight hours went by in a flurry of activity.

Sandy wanted to photograph Ricardo's map so that the fragile original could be folded up again and returned to its hiding place in Ricardo's amulet.

There were last-minute purchases to be made, and long-distance phone calls to be put through. They telephoned Ricardo's mother, to let her know of his change of plans. They spoke twice more to Gonzalez, who insisted upon making his own arrangements for their comfort and convenience in Mexico.

Their plane left after midnight, so only Bert had driven in to see them off. At the last moment he pulled a small, carefully wrapped package out of his pocket.

"Almost forgot this," he muttered, handing it to Sandy. "It came for you yesterday. Want me to keep it until you get back?"

"Never mind," Sandy told him. "It doesn't weigh much, whatever it is. I'll take it along."

And then they were off, waving through the windows as the plane taxied down the runway.

"Now is the moment to remember all the things we've forgotten," Ken said, settling back in his seat and grinning at Ricardo across the aisle.

"Now is the moment to see what's in this package," Sandy said. He pulled off the paper. "Megabucks!" he exclaimed.

"Mega-what?" Ken asked.

"Don't you remember the last book we read about Rick Brant and Don Scott?" Sandy asked.

"Sure," Ken said. Only recently they had both read an account of the South Sea expedition undertaken by the two young men whose adventures had landed them in dangers as desperate as any Ken and Sandy had ever experienced. "Oh!" Ken added. "Of course! Megabucks are the miniature radio transceivers they design and build! You said you were writing Brant and Scott a letter about them."

"I did-and they've sent us some to try out. One for each of us, and a spare in case one fails." Sandy was reading the letter he had found inside the package. "They've read some of our stories, and think we might make use of these sometime. They say," Sandy read from the letter, "'if you ever have to do another tailing job like the one in The Mystery of the Iron Box, these things might come in handy.' Look at them, Ken. Aren't they great?"

Each little transceiver was scarcely larger than a cigarette pack. Its microphone was small enough to be built right into the tiny megabuck case. Its earphone was a little plug that fitted into a listener's ear, as if it were a hearing aid.

"It's too bad we can't try them out right now," Sandy said, when he finally packed the little mechanisms back into their box.

They all slept, finally, worn out by the exertions of the past few days. And then, almost before they knew it, the big plane was dropping down through clouds lit by a rising sun into a great saucerlike plain. Out of it rose ancient Indian pyramids and the sparkling new skyscrapers of Mexico City. Ricardo's face showed his pleasure at seeing his homeland after so many months' absence.

"I don't see Ramon," Ken said, as they moved slowly down the ramp on their way to the customs building.

They were stepping through the door, Ken in the lead, when a voice spoke their names.

"Senior Holt? Senior Allen?"

Ken halted. The man who had addressed them wore a crisp, brown police uniform. His shoes were highly polished. His cap was set at a jaunty angle above smiling young eyes. Ken smiled back at him, and identified himself and his friends.

"Bueno. And I am Lieutenant Rodriguez." He saluted smartly. "Captain Gonzalez regrets very much that he could not meet you himself, and has delegated me to serve in his place." He unbuttoned the pocket of his shirt and handed Ken the envelope he took from his pocket. "This is a letter from him. While you read it, I will have your baggage cleared and transferred to the San Cristobal plane, if you will be so good as to let me have your papers." He smiled. "The plane does not leave for half an hour. But I will take you across the field in the car, and I will do my best to complete the formalities in a few minutes. I would not wish to face the captain if you missed your plane because of any lack of efficiency on my part."

After the young officer had left them, the boys found a quiet corner in which to read their letter.

"Amigos," Gonzalez had written, "it is necessary that I leave at once for Merida, Yucatan, in the line of duty, so I will be unable to welcome you in person. I hope Lieutenant Rodriguez, who gives you this letter, will look after you well in my absence.

"If you should need to communicate with me, I can be reached during the next several days through the MeVida Police Department. I hope you will enjoy the Hotel Altamira in San Cristobal, where you should find an envelope I mailed to you yesterday. It contains a photostat of an old plan of the Obregon hacienda's walled enclosure, showing the location of the buildings that once stood within it. Also in the envelope is a modern large-scale police map of the San Cristobal area. You will find it more useful for sightseeing than an ordinary road map, because it will show you all the smaller roads and trails of the region.

"Captain Arturo Morro of the San Cristobal police will greet you at the airport there. He has promised to arrange for the rented car you said you would want. He is a man who does not forget a promise.

"Ask Lieutenant Rodriguez for anything you may need. He brings you my best wishes. It is possible I may be able to travel back to Mexico by way of San Cristobal, and there have the pleasure of watching you hunt for treasure. If not, I will expect you to stop in Mexico City before returning home, and relate to me the whole story of your adventure."

"What a break!" Sandy said. "Why, if we have a plan of the hacienda enclosure, we shouldn't have any trouble at all. Well just superimpose ours on it, and then we ought to know exactly where those tunnels are."

Lieutenant Rodriguez was as good as his word. He was beside them within a few minutes, to report that their baggage had been cleared and that the car stood ready to take them to the far side of the big field where the San Cristobal plane was waiting. He didn't leave until they were aboard it.

They were still eating breakfast when the plane came down at the large city of Puebla, to drop a few passengers and pick up others. The next leg of the flight, to Oaxaca, was slightly longer. After that stop the plane flew close to the Pacific coastline for miles, dropping down into the intense tropical heat of Tehuantepec, and then flying on to the bustling modern city of Tuxtla Gutierrez, the last stop before their destination.

From Tuxtla Gutierrez to San Cristobal de las Casas was only about fifty miles, but they could guess what a slow journey it might be by car, as they watched the land rise steeply into a range of heavily wooded mountains. High among those mountains, at an altitude of seven thousand feet, lay the town whose long name Ken and Sandy already found themselves shortening to San Cristobal.

The sun was fiercely hot when they stepped out of the plane and stood uncertainly for a moment on the paved apron of the San Cristobal airport. But when they moved into the shadow of the nearest building, they felt the sharp coolness that promised chilly nights.

Almost immediately, once again, a strange voice was saying, "Senor Holt? Senor Allen?"

The speaker was a huge bear of a man dressed in faded khaki trousers and shirt, and wearing a faded and shapeless peaked cap on his grizzled head. "I am Arturo Morro," he said genially, in a voice that was clearly little accustomed to English. "My friend Captain Gonzalez has told you of me, no?"

Ken extended his hand, introducing himself and his friends.

Captain Morro's broad face spread in a smile as he heard Ricardo's name.

"Ah, you are Mexican, no?" he demanded.

"Yes," Ricardo told him. "My home is in Rio Claro."

"Bueno, bueno" The officer patted Ricardo's shoulder, and rattled off a torrent of Spanish so rapid that neither Ken nor Sandy could catch a single word. He stopped as abruptly as he had begun, and turned once more to the boys. "I am saying that of your language I know very little. It will be more easy then, I say, if I speak to your friend in our own language, and he can change it into English. You agree?"

"Of course," Ken assured him.

The policeman motioned Ken and Sandy to follow him, and made off with Ricardo toward a small, slightly battered European car, talking volubly in Spanish as he went.

"This is the car he has arranged for us to rent," Ricardo said over his shoulder as they neared the vehicle. "The papers for the car are at the hotel. He says you can sign them at your convenience. The man from the car rental agency will drive us back into town," he added.

The little car looked even more battered at close view than it had from a distance. But the young man waiting beside it seemed brisk and efficient. And when he jumped into the driver's seat, and started the motor, it ran with a satisfactorily smooth purr.

Captain Morro performed the introductions, and then made his own good-bys, with many earnest expressions of his wish that they call on him at the police station for anything they might need.

"He says the station is on the south side of the plaza," Ricardo translated, "diagonally opposite our hotel on the west side."

They all shook hands, thanked him, and assured him they would see him again. And finally they were ready to drive to their hotel, their baggage packed snugly in the rear of the little car.

The airport was only half a mile from the city. Soon the car was threading its way through narrow cobblestoned streets, among laden burros, trucks, and buses.

"No wonder Ramon said this was an interesting town," Ken said quietly to Sandy, beside him on the rear seat. "At least half of the people on the sidewalk are wearing native costumes. We've never seen anything like them before. The people in Mexico City dress the same way people do in New York or Chicago or Brentwood. But here-!"

"I see them." Sandy was peering out of his side of the car. "Look at those straw hats with big ribbon tassels hanging from the crown! And those little pink-and-white-striped jackets or shirts or whatever they are that some of the men have on, with white shorts!"

There seemed to be several different kinds of costumes. Some of the men they saw wore longer white garments of heavy wool. Others wore black wool striped in white.

Most of the women's skirts were long and full, some topped with embroidered blouses, some with the same blanketlike garment the men wore, with a slit in the center which permitted them to pull it on over their heads. Burdens were balanced on their heads, or hung from bands that passed around their foreheads. Men and women both were shod with heavy sandals, or walked barefoot along the crowded sidewalks past open shop fronts.

The driver swerved into a big square, with paved walks and neat beds of flowers set in a formal pattern around a central bandstand. He gestured, and spoke to Ricardo.

"We are coming into the square-the plaza-from the north side," Ricardo translated. "He wishes you to know that the traffic around the plaza is one-way -counterclockwise."

"We’ll remember," Sandy assured him.

The Altamira Hotel, where Gonzalez had made reservations for them, was an old building with long balcony-fronted windows reaching almost to the sidewalk. It had probably been erected, Ken thought, in the days when die Spaniards still ruled Mexico.

The driver pulled up smartly in front of it.

"He wishes to know," Ricardo told the boys, "if you will need a lesson in driving. I have told him you know a great deal about cars."

Sandy had been leaning forward during the last few blocks, assuring himself that there was nothing about the mechanics of this particular car that was strange to him. "Tell him well manage all right," he said. "But ask him where we should leave the car when we're not using it."

The driver answered Ricardo's question with a flood of Spanish. Ricardo translated it into briefer English.

"There is a garage across the square, where we should leave the car when we no longer want it, or if we need service. But we can leave it here as long as we wish," he explained.

"O.K. Thanks," Ken said. Then he repeated in Spanish, to the driver, "Bueno. Gracias"

The driver got out from behind the wheel, shook hands all around in the way Ken and Sandy had already come to know as typically Latin, and walked off across the square just as a plump, middle-aged man emerged from the hotel. He was dressed in sober black, but the pin in his tie sparkled brightly and his smile was warm. "Ah, senores!” he said. "You have arrived. Senor Holt, Senor Allen, and Senor Montez, no? I am Jose Lavaca, manager of the Altamira, at your service."

He barely paused for brisk handshakes, and then he summoned a young boy and ordered him to carry the luggage of the new arrivals to their room. "Numero quatro," he told the boy. "That is number four," he explained. "It is our biggest room. We hope you will be comfortable. A captain of the police of Mexico City has asked that we take very good care to make your visit pleasant."

"I'm sure we'll enjoy ourselves," Ken told him, as the manager gestured them to follow him inside.

The Altamira's lobby was small and rather dismal. But just beyond it, through open double doors, was a flower-filled patio with a small fountain at its center.

Jose Lavaca presented his registration book with a flourish.

"Is there any mail here for us?" Ken asked, as he signed it.

"Ah, si!" The plump figure whirled around toward an old-fashioned desk and unlocked a drawer with a key he took from his pocket. "I have put it in a safe place," he informed them.

The envelope he handed Ken was large and brown and thick. Ken opened it as soon as they were alone in their big room with its three beds, its massive dark wardrobe, its stiff uncomfortable chairs.

"Here's a letter from Ramon," he said, opening the first of the folded sheets. "It just seems to repeat the stuff he told us about the Obregons over the phone. We'll read it more carefully later. And here's the road map Ramon said he'd sent. And here's the photostat of the plan!"

"Spread it out here, Ken," Sandy urged, "so we can all get a good look at it." He whisked his camera case from the top of a small table as he spoke, leaving its surface bare.

Ken opened the stiff photostat and flattened it out. They all bent over it.

The reproduced drawing was clear and simple. Double lines represented the hacienda's wall. Neat rectangles inside them, labeled in Spanish, indicated the buildings the wall surrounded.

"And here's our photograph of Ricardo's map," Sandy said, taking it from his pocket. "We'll have to do a little figuring, to bring the different scales of the two drawings into line. But if each of the four dots on this is one of the corners of-"

"Which it isn't," Ken said suddenly. "This plan of the hacienda enclosure is a rectangle. The four dots on Ricardo's map form a square. The two things don't match at all! So we haven't any way of knowing what those four dots stand for-and absolutely no way of finding out where, on the whole Obregon property, those tunnels might be!"

CHAPTER VII

THE RUINED HACIENDA

"Bur-but-!" Anger and disbelief both sounded in Sandy's voice. "There must be some mistake!"

"There's a mistake, all right-and we made it," Ken said grimly. "Thinking all we had to do was come here, spend five minutes with a tape measure -and then start digging straight down at the right spot."

"But, Ken-Sandy-it is hopeless then?" Ricardo asked faintly.

"It looks like it," Sandy admitted. "Me and my bright idea about those four dots!" he added disgustedly.

"Unless-" Ken began suddenly, and reached for the letter from Ramon he had put aside earlier.

"That's right!" Sandy moved so that he could read it too. "Maybe Ramon dug up some information that will put us on the right track."

Ken read the letter through aloud.

At the end of it they stared at each other. The only fact which Gonzalez had not previously told them was the size of the original Obregon property. The family had once owned about twenty-five thousand acres-land which spread about equally in all directions from the walled enclosure at its heart.

"Anyone for digging up twenty-five thousand acres?" Ken asked, with a wry grin. Then he saw Ricardo's look of misery, and realized that the boy was feeling personally responsible for the wild-goose chase that had brought them all such a long distance. "But don't let's lose our sense of proportion," he went on hastily. "We've all been planning to come to Mexico, and looking forward to it. So far as Sandy and I are concerned, we'll probably find this part of the country the most interesting we've ever seen. And we all want to go over and look at the ruined hacienda at least, don't we?"

"Oh, sure," Sandy said flatly. "Let's all rush out and admire the fascinating sight of a bunch of crumbling adobe walls." He sat up slowly from the bed where he had thrown himself a few minutes earlier. "Though, of course," he went on slowly, with a note of hope in his voice, "we really might see something out there that would give us a clue."

"I think," Ricardo said carefully, "that we would be quite safe to make the guess that the tunnels are inside the enclosure. If the Obregons were very cruel to their peons, and knew always that a revolt was possible-surely they would not build secret tunnels, and hide anything valuable, in the open fields where the peons could watch."

"That makes sense, Ricardo," Sandy said. "Let's take another look at this plan."

He headed for the photostat still spread flat on the table.

"If it is not a big enclosure," Ricardo went on, while Sandy calculated the size according to the map's scale, "we could dig trenches in it. You know, the way archaeologists do when they are exploring a new site."

"There's not much use trying it, Ricardo," Sandy said, interrupting him. "The enclosure measures about fourteen acres."

"Fourteen acres!" Ricardo repeated. He shook his head. "No-to dig trenches across so much land- no, for us it would not be possible."

"Not in the length of time Pop expects us to be away from the Advance" Ken agreed. "Of course if we didn't have to get back home for eight or ten years-" He gave up his feeble attempt at cheerfulness and got to his feet. "Come on. Let's stop sitting around feeling sorry for ourselves. Let's drive out to the hacienda and take a look. And then tomorrow we can do some of the serious sightseeing we originally planned to come to Mexico for."

According to the map of the region which Gonzalez had sent them, the hacienda was about ten miles from San Cristobal de las Casas. Sandy took the wheel of the little car, with the others squeezed in beside him, and they set off.

Once they had left the town the road was un-paved, dusty, and barely wide enough for the small vehicle they were driving. But they had it all to themselves as they followed it along the bottom of narrow valleys between green hills. Occasionally it rose sharply, in a series of hairpin turns, right over the top of a ridge and down its other side. Pine trees, their trunks studded with parasitic orchids, edged the road for long distances. Only occasionally was a valley broad enough to accommodate a cultivated rice field or a stand of grain.

They passed several small villages, each consisting of no more than a dozen thatch-roofed, mud-floored huts. They rattled over the stony beds of dry streams, and once or twice crossed a small bridge over a trickle of water that would obviously swell into a small raging river when the rainy season began.

Ken looked up from the map. "I figure we must be within two miles of the hacienda by now," he said.

About half a mile farther on, the road seemed to run head on into a steep, heavily wooded hill, but at its foot it swung sharply to the right. For another half mile they hugged the base of the rise, riding in the deep chilly shadow of the hill itself.

Then they drove out of the shadow and were once more in the hot, dazzling sunshine. The wooded hill dropped behind them as the road made a wide sweep toward the left, along a valley that seemed to run on for miles until it ended at a wall of mountains. To their right, only a few thousand feet away, was a low knob of land whose slopes were covered with young trees.

"That's fairly new growth," Ricardo murmured. "That hillside probably was cultivated not long ago."

"Until the Obregon peons got tired of being treated as slaves, and revolted," Ken suggested. He leaned past Ricardo to get a better view. "Hold it, Sandy!” he said suddenly. "The hacienda's up there -or what's left of it."

Sandy halted the car.

On top of the low hill the remains of a wall rose like a crumbling battlement above the trees at its foot. Taller, older trees spread their branches above it on its far side. Portions of the wall had broken away, leaving the top uneven. A tower rising at one corner had been partially destroyed.

They stared at the ruin for a moment before Ken said, "Well, we can't really see very much from here. Let's find out if the map shows the best way to get up there."

With his finger on the rectangle that represented the hacienda enclosure, Ken located their position. "Looks as if we ought to drive on a little farther, to a point where we'll be opposite the entrance in the west wall." He pointed to the word entrada printed on the map.

A few minutes later they stopped the car again, and got out to look up at the gap in the wall that Ricardo had spotted.

Sandy picked up the binoculars they had brought, and aimed them. "I guess that's the gate all right. At least it's a gateway. I can see the remains of a gatepost on the right side of the opening, and a piece of hinge still attached to it." He lowered the binoculars and looked at the steep, overgrown hillside separating them from the entrance he had been studying.

"I suppose there was a road up there once," he said, "but there aren't any signs of it any more. If we're going up we'll have to walk."

"I think it is not more than one thousand feet," Ricardo said.

They went up in single file, finding their way slowly among the trees and bushes that barred their way. The heat, the stillness of the air, the steepness of the hill made them all feel that Ricardo had underestimated the length of the climb. But finally, hot and out of breath, they stood before the opening that must once have been an imposing gateway.

For the first time they could see the full massiveness of the wall itself. It had risen some twenty feet into the air, tapering only slightly from a base eight feet thick.

And now, for the first time, they could sense the complete desolation of what had once been the Obregon hacienda. Piles of crumbling and weathered adobe were everywhere-at the foot of the walls on either side of where they stood, and beneath the towering trees that filled the enclosure like so many tall, silent, green ghosts. The air was very still. Even the leaves were motionless.

Suddenly a bird squawked raucously somewhere not far away, and they all jumped at the sound. Only their startled reaction made them realize that they had been standing at the threshold of the ancient gate for several long seconds. As Ken became aware of his own vague reluctance to step inside the enclosure, he knew the others were feeling it too.

He cleared his throat. "Shall we go on in?"

"What was it Ramon said about a ghost?" Sandy asked. And then he grinned quickly, as if he felt the need to prove to the others that he was joking. "Let's take a look at that plan first," he went on, in a more businesslike voice.

They unfolded the photostat Ramon had sent them, showing the original arrangement of the buildings within the Obregon walls.

"We're here, in front of the gate," Ken said, pointing to the spot on the plan.

"The main house was just inside, to the right," Ricardo pointed out, touching one of the rectangles marked on the plan. The words lettered on the rectangle were La Casa Obregon, and the rectangle itself had been drawn with double lines, making one rectangle inside the other. "The house was built around a patio, I think," Ricardo added. "That must be why it was drawn that way-and most Spanish houses were built in that style."

Each of the other ten rectangles on the plan was also marked. In the northwest corner, its rear wall apparently part of the enclosure wall itself, was a figure labeled church. In the eastern half, opposite where the boys stood, were those marked stables, storage barns, servants' quarters, bakery, and smokehouse. Close to the big house itself was one marked school.

"Well," Ken said, when they had studied the arrangement of buildings, 'let's go inside and look around. Let's see how many of the buildings we can identify from their ruins."

They looked for the Obregon house first, and found little but mounds of debris around a tangle of bushes and weeds and small trees that had obviously once been a patio garden. Only a portion of one wall was left standing-part of a large fireplace and a fragment of the chimney that had once risen above it.

A smaller pile of weed-grown rubble marked the spot where the school had stood.

Sandy shivered. "It's chilly in here, in all this shade," he said, his voice instinctively lowered. "Have you had enough?"

"As long as we're here," Ken said, "why don't we at least take a look around and see if we can't find something that might correspond to the four dots on Ricardo's map? We'd never forgive ourselves if we went off without even making the effort."

"The only way we could ever see any pattern in this jungle is from above it," Sandy said. "But the interior of that corner tower is gone, and we can't get up to the top."

"There might be something left of the church," Ricardo offered. "It probably was built better than many of the other buildings. It may even have been built of stone. And perhaps the men who destroyed the hacienda would not try to destroy a church."

They made their way slowly across the big enclosure, stepping around piles of rubble and fighting their way through tangles of vines, until they stood before what had been the wide front doorway of the church.

Ricardo had guessed correctly. The building was roofless, but three of its walls had been made of stone, and were still standing. Only the back wall, which was also part of the wall around the whole enclosure, had been constructed of the clay bricks called adobe. In that wall was a gaping hole through which they could see distant fields and hills.

Ken led the way slowly into the ruined interior. The floor had been laid with flagstones, but most of them were covered over with drifting dust in which weeds had taken root.

"Look!" Ken pointed suddenly. "There's a stairway going up along the wall back there! Maybe we can get a view of the whole place from the top of it."

Each step of the stairway was a single heavy slab of stone, fitted snugly into the massive stones of the wall. The stairway ended at a platform, only a few feet below the wall's top.

Sandy studied the stone steps, unsupported on their outer edge. "They look secure enough," he admitted. "I guess they'd take our weight." He started up the flight, with Ken behind him and Ricardo bringing up the rear. They walked slowly, keeping close to the wall.

When they stood together on the platform at the top, they aft took a deep breath. And then they turned their eyes to the whole walled enclosure spread out beneath them.

"Well?" Sandy asked. "Does anybody see four things that might have shown on Ricardo's map as four dots in a square?"

"I can't," Ricardo admitted reluctantly.

Suddenly Sandy became aware that Ken was kneeling on the platform floor. "What's the idea?" he demanded. "We're supposed to be-"

"I know," Ken said quietly. "But look here a minute." His finger indicated a wide crevice between two of the big stones that formed the floor.

Ricardo bent over to peer into the crevice. "The ends of several cigarettes," he said. "It is not surprising, I think. Perhaps tourists often find their way to these ruins. Someone may have smoked those cigarettes many weeks ago. It is the dry season, you know, and-"

Ken interrupted him. "This one hasn't been here for weeks. Get down closer, both of you, and look at it." He touched one of the cigarette butts, moving it slightly.

A tiny wisp of smoke rose from its still-smoldering tip.

"Our tourist-if that's who it was," Ken went on, 'left here only a few minutes ago, or less."

"Get down closer, both of you, and look at it," Ken said

"Funny," Sandy muttered thoughtfully. "You'd think we would have seen him."

"Not necessarily," Ken said. "He could have slipped through that big gap in the back wall. He'd be outside the enclosure then. But what puzzles me is why he left. Most tourists, in as lonely a spot as this, at least say hello to any other visitors they run into. And from here anyone could have seen us as we came through the gate and over here to the church. My guess," he concluded slowly, "is that he-or she -didn't want us to know we'd been under observation."

CHAPTER VIII

ATTEMPT NUMBER FOUR

"Under observation?" Sandy repeated blankly. "You mean someone was spying on us and then rushed off so we couldn't catch him at it?"

"Doesn't it look that way to you?" Ken asked.

"Now listen!" Sandy burst out. "Ghosts of some long-departed Obregons I could put up with. But let's not add a live ghost to the picture just to make things worse!”

"What's your explanation of the cigarette?" Ken asked. "Look at it-it's burned away an eighth of an inch during the short time I've been looking at it. That means it couldn't have been lying here for more than a couple of minutes or it would have burned entirely away by now. So it must have been dropped here when we were already approaching the front of the church."

"So?" Sandy demanded challengingly. "Does that prove it wasn't dropped by an ordinary tourist?" He turned the cigarette over. "Did you notice it's an American brand? Doesn't that suggest a tourist?"

"Why should an ordinary tourist take off in such a hurry?" Ken asked. "And why didn't he-or she- leave by the front door or where we would have seen him? And why should anybody climb up that mound of loose rubble, and go out through that hole in the back wall, unless he had some good reason- unless he didn't want to be seen leaving the place? Let's see if we can catch a glimpse of him," he added quickly.

He started hurriedly down the stone steps, the others behind him. A moment later they were scrambling up the barrier of rocks and earth that partially blocked the gaping hole in the rear wall of the church.

Through the hole they looked out on the overgrown slope that fell away from the walled enclosure toward the north. They could see the surrounding hills for a distance of a mile or more. No human beings were visible anywhere. But the slope just below them was a tangle of low bushes and vines which might conceal half a dozen persons.

Ken cupped his hands around his mouth and shouted. "Hello! Is anyone here?"

The rustle of wind in the bushes was the only answer to his voice.

"Do you think the person who left that cigarette could already be too far away to hear me?" Ken asked.

"N-no," Sandy said hesitantly. "I wouldn't think so."

No one said anything for a long moment. They stared at each other soberly.

"Is there any reason for hanging around here any longer?" Sandy asked abruptly. There was an edge to his voice. "I think we've seen all there is to see."

Ken glanced back toward the stairs down which they had come a few moments before. "I didn't take a look around from that platform," he began.

"You don't have to," Sandy assured him. "Ricardo and I did. And there's absolutely nothing that could be those four dots on the map. Take our word for it -and let's get out of here." He sounded jittery, as if the combination of gloomy ruins and the mysteriously smoking cigarette butt was too much to stand.

None of them had anything to say as they made their way back through the church and past the other ruins that lay between them and the gate.

"I'll drive," Ken said when they reached the car. "I'd like to see what this car feels like."

"And you'd also like to make us another speech about that cigarette," Sandy said. But the edge had gone from his voice, now that they were outside the walls once more. "You just have to learn to put up with him, Ricardo," he added. "He's a stubborn guy."

"I'm stubborn enough," Ken admitted, "to want to talk about that cigarette in connection with all the things that have happened to Ricardo since somebody broke into his room."

"I knew it!" Sandy said. "I knew itl You are now going to tell us that somebody has been after Ricardo's amulet, and the map inside it, ever since that day! But save your breath, Ken. Didn't Ricardo explain to us that if anybody knows enough about his amulet to know there's a map inside it, that person would also know enough to ask Ricardo for it?"

"I know," Ken said quietly. "Ricardo is waiting to turn the amulet over to the person who asks for it by quoting the words carved in the silver. But I'm suggesting that somebody is after that amulet who doesn't have the right to ask for it, and doesn't know how, but who is determined to get it just the same."

Sandy opened his mouth.

Ken held up his hand. "Just let me make my speech," he said. "I've got quite a theory worked out in my head, and I'd like to explain it-without interruptions." He grinned briefly. "You can both present the brilliant arguments that will knock it into a cocked hat when I'm finished. O.K.?"

Sandy sighed elaborately. "I told you, Ricardo- he's a stubborn guy. All right, Ken. Go ahead. Just try to keep it as brief as possible, will you?"

"I will listen, Ken," Ricardo said earnestly.

"Good." Ken eyed him gratefully. He took a deep breath. "My story starts during the Mexican Revolution of 1910," he began, "when the Obregon hacienda was attacked."

"Brief, I said," Sandy muttered.

Ken ignored him. "I think Ricardo's grandfather was inside the walls when the attack started," he went on. "I think he was a trusted employee who knew that the Obregons had buried the family wealth when it was clear that the peons were revolting. I think he slipped out of the hacienda, at the beginning of the attack-perhaps to try to bring help, but also for another reason. I believe the Obregons counted on him to look after their affairs in case help didn't reach them in time, and the family was wiped out

“We know the family was wiped out," Ken continued. "But the Obregons were Spaniards, and I'm guessing there was another branch of the family in Spain-or, at any rate, that there were people somewhere who were legitimate Obregon heirs. I'm calling them the Spanish branch of the family for convenience. And I think the Obregons of San Cristobal, realizing that they were facing extinction, worked out a scheme to save some of their wealth for heirs who were safely away from the hacienda.

"The scheme involved two maps," Ken elaborated. "One showed the detailed location of the treasure in certain underground tunnels. That's the one Ricardo's grandfather kept hidden in an amulet, according to instructions. The other map showed the location of those tunnels on the Obregon property. Both maps would be needed in order to find the treasure. Probably four dots appear on each one-and when the dots are superimposed, the exact location of the treasure can be found."

"Fascinating!" Sandy murmured.

Once more Ken ignored him.

"Now this is what I think happened," he said. "Ricardo's grandfather, following instructions, mailed one map to the Obregon heirs. Along with it he sent a letter explaining that he had a second map, and also explaining how it could be obtained from him- that is, by quoting back to him the words carved on the amulet."

"But why did no one ever claim the amulet?" Ricardo asked.

"I don't know," Ken admitted. "I'm guessing that the map and letter were discovered only recently. And I'm guessing that the person who now has these things doesn't have all the information he needs to claim the amulet openly."

"But he just happens to know there is an amulet in Ricardo's possession and that it contains a key map to a valuable treasure." Sandy's sarcasm was obvious.

"It's not impossible," Ken defended. "Suppose that for some reason Mr. X, the man who has the other map, knows only that the Montez family has the key map and that the family lives in Rio Claro. Thats where he'd go first, and that's where he'd learn that Ricardo, the only living male Montez, was in the United States. It would be simple to discover where Ricardo was staying and then to burglarize his room. After that failure, Mr. X could easily watch Ricardo's movements, follow him to Brentwood, and make another attempt. Failing there, Mr. X could follow us to Dad's place and make a third futile try. Then he could follow us to Mexico-or beat us down here, since he could easily guess our destination-and be ready to take up the chase as soon as we arrived."

Sandy snorted. "Suppose you explain why the mysterious cigarette smoker-your Mr. X, I presume -didn't make a try at getting the amulet from Ricardo at the hacienda. The place was deserted, and Mr. X has no objections to using guns, I seem to remember."

Ken shrugged. "There are a couple of possible answers to that. Mr. X could have seen us being greeted by the chief of police and he might figure it isn't smart to make an open attempt to rob anyone on such good terms with the local authorities. Or maybe he didn't have his mask handy, and didn't want to show himself to us.

"After all," he reminded the others, "none of us knows what Ricardo's past assailants-that includes the men in Dad's apartment-really look like. If we found out, we'd be a danger to them-unless they killed all three of us, of course, and they probably don't want to risk a triple murder charge."

"You seem to know Mr. X and his accomplice pretty well," Sandy muttered.

"I'm not trying to pretend that I know anything about them, or that this is anything but a theory,' Ken said. "But, so far, I think the theory fits the facts. There's another possible explanation for why he-or they-didn't jump us back there," he added. "Mr. X probably knows our map is useless to us by itself. And maybe he thinks we won't take such good care of it after we've found that out. So he may just be waiting for us to get careless."

Ken was driving around the plaza as he finished speaking. He drew up in front of the hotel and turned off the ignition.

"Well?" he said, after a moment of silence. "Do I take it you both agree with me?"

"No, I do not agree with you," Sandy said firmly. "You have no proof for anything you said. You've strung together a lot of coincidences, and turned out a yarn that would make a great movie. But your only real piece of evidence-a smoldering cigarette- could have a dozen perfectly logical explanations. I'll admit I felt a little jittery back there in the ruins. In a creepy place like that it's easy to believe somebody's spying on you. But here in the middle of town, with plenty of people around, all I feel is hungry. Gentlemen, I suggest we eat."

Ricardo hesitated, one hand on the door handle. "What you said is most interesting, Ken. But it does sound-well-"

"Melodramatic is the word you're searching for, Ricardo," Sandy told him. "You coming, Ken?"

Ken grinned at him wryly. "My theory isn't going to fade away under the influence of food," he said. "But I know better than to try to argue with you when you've gone several hours without sustenance."

Two minutes later they were unlocking the door to their room and Sandy was audibly planning the assortment of sweet Mexican rolls he hoped to be consuming with his coffee very soon.

"And later, for dinner," he murmured, picking up his bag and opening it on his bed, "I think I might have some-" He cut his words off short. "Hey!” he said an instant later. "Have either of you been in my bag?"

"Of course not," Ken told him. "None of the bags have been opened since we arrived. Why?"

"Because," Sandy said slowly, in a puzzled voice, "this isn't the way I pack. I don't put my socks on top and my- Somebody's been going through my things! Take a look at your bags while I check my camera case," he added quickly.

Ken and Ricardo both opened their suitcases.

Ricardo gave a faint gasp. "My things are also not as I packed them!" he said.

"This camera case has been searched," Sandy announced angrily. "I don't pack my gear like this!”

"Someone's been through my bag, too," Ken said quietly. He sat down on his bed and looked up at the redhead towering over him. "How many coincidences do you have to be hit with before you begin to notice them?" he asked.

CHAPTER IX

THE BOYS TAKE THE OFFENSIVE

"Or course," Ken went on, with elaborate politeness, "if you prefer to believe that an ordinary sneak thief happened on our room while we were gone-"

Sandy interrupted him. "Don't be silly," he growled. "Nothing's missing-at least none of my stuff. You lose anything, Ricardo?"

Ricardo shook his head. "My things are all here. They are only a little mixed up."

"Mine too," Ken said. He walked to the door and looked at its old-fashioned lock. "Practically any skeleton key-in fact, even a hairpin-would unlock this." He opened the door and looked along the corridor that ran around the hotel's inner patio. "There's a door into the street from the end of this corridor," he said, "right up at the corner there. And any ordinary sneak thief-"

"All right-that's enough," Sandy said. Tve told you I don't think an ordinary thief was responsible for this. I admit it: I think somebody came in here looking for the map. And if you want to say it was the same two men who held us up at your father's apartment-"

"Oh, no." Ken grinned. "I don't. I think it was only one of them. The other was waiting for us at the hacienda, to see what we'd do-to watch us discover that our map was useless."

Sandy threw up his hands. "All right! One of them came in here. One of them was at the hacienda smoking American cigarettes. Mr. X and Mr. Y, I presume. They are after the map the Montez family has been guarding for three generations. So let's say we all accept your theory, at least tentatively. The question is what do we do about it?"

"I don't know," Ken said slowly. "If this was happening at home- But wait!" he said suddenly. "I think I've got it! Let's let them have a copy of the amulet map!"

"Give them a copy of Ricardo's treasure map?" Sandy's outrage sounded in his voice. "That's a fine way out-that is!"

"I could not do that, Ken," Ricardo said. "My father-"

"Wait a minute," Ken said. "I haven't explained what I really mean yet. But tell me this before I go on -what do you think Mr. X and Mr. Y would do if they did get hold of a copy of Ricardo's map?"

Sandy answered him promptly. "Go right out to the hacienda-presumably with the other map or information they already have-find the treasure and take off."

"But now tell me this," Ken broke in. "What do you think those gentlemen would do if they got hold of an imperfect copy of the map? A copy, say, on which the position of four dots had been slightly changed."

Sandy stared at him blankly for a moment, and then a broad grin broke over his face. "Ken, you've hit it!" he exclaimed. "What a plan! It's a masterpiece! Do you get it, Ricardo?" He turned eagerly toward the Mexican boy.

"I am not sure," Ricardo said uneasily. "You think you will make changes in my map, no? And then let them have it?"

"No," Ken said quickly. "We wouldn't touch the original map, of course. But we'd make a new copy of it-a copy that would not be quite the same as the original."

"To lead them to the wrong place?" Ricardo asked.

"Exactly!" Sandy told him. "They'll think they can find the treasure-and they'll dig and dig and dig. Only they'll be digging in the wrong place!"

"But will they not begin to suspect that the map we give them is wrong?" Ricardo asked.

"In the first place we won't be giving it to them," Ken explained. "We'll let them steal it. So at first they'll be pretty sure they've got the right thing."

"But, in the end, when they are sure the map is not right, I think they will come looking for me again," Ricardo said.

"And that's just what we want them to do," Ken told him. "We want them to go rushing off to Rio Claro looking for you, because that's where they'll think you are. Only you won't be there. You'll still be here with us-and we'll be locating the treasure ourselves. Because," he concluded, "the minute they start digging in the wrong place, we'll know the exact location of the right place!"

"We will?" Ricardo looked completely confused.

"Sure we will!" Sandy took it up. "Suppose we shift the position of those dots the equivalent of a thousand feet north of their real position-then we'll know that the proper place to find the treasure is exactly one thousand feet south of the spot where those men start to dig!"

Understanding dawned on Ricardo suddenly. "Of course!" he said. "Of course!"

"And when they leave," Ken said, "well get right to work. We can do a little spying too, you know. We'll have been watching them the whole time. We'll know right where to dig. And we'll finish our treasure hunt before they find out you didn't go back to Rio Claro, after all."

Ricardo grinned. "I think it will be pleasant to watch them dig and dig and dig and find nothing. How do we let them steal the map?" he went on. "We will make it the way you say, and then leave it here in our room, no? Then the next time they come to look through our things, they will find it."

"That might not work," Ken said reflectively. "They might never try to burglarize this room again. They may be convinced now that we always carry the map with us. No-we'll have to think of something else." He sat down on the edge of the bed and leaned forward, elbows on knees, one hand plowing through his hair. "If we only knew who they were," he muttered, "we could figure out how to leave the map in a place where they'd think they were being clever to take it away from us."

"Could we not just walk around San Cristobal tomorrow, and watch to see who followed us?" Ricardo suggested. "Do you not think they would follow us-and that by looking always behind we could find out who they are?"

Sandy shook his head. "Too risky," he said. "We don't want them to suspect that we know anything about them-and they might catch us looking over our shoulders. Come to think of it," he added abruptly, "they may be too smart ever to steal the map!"

"But this is what you think they tried to do several times, is it not?" Ricardo asked.

Ken had been nodding at Sandy. "I see what Sandy means," he told Ricardo. "Sure, I do think they tried to steal it when you were in the United States. Then, maybe they thought you didn't know what was in the amulet, and that you'd think somebody had stolen it because it was silver. That's probably why they took your money that first time-to make it look like an ordinary robbery."

"And this is what I did think-then," Ricardo admitted.

"But now that we're down here," Ken pointed out, "they must realize you know about the map. Therefore, if the map is stolen, you might go straight to the police and just tell them to watch for anybody who turns up at the hacienda with a shovel."

"But you said-" Ricardo began.

"I know," Ken said. "But I was wrong. I realize now they won't try to steal the map outright. They'll just try to get it long enough to copy it, and then put it back. They don't want us to know that anybody has it."

"Exactly," Sandy agreed. "So what we have to do," he added, with a wry grin, "is perfectly simple. We just have to leave a fake copy of the map in some place where Mr. X and/or Mr. Y can get at it long enough to copy it, and then put it back. And we must arrange for this to happen in such a way that we see them doing it, so we know who they are." He shook his head. “Sure-it's perfectly simple! Only just exactly how do we go about it?"

"It would help if we could learn who they are, would it not?" Ricardo asked earnestly.

"Yes," Ken said, mirroring Sandy's wry grin. "It certainly would help. Of course I suppose we could ask Captain Morro to lend us one of his officers-" He stopped, suddenly aware that Ricardo was beaming excitedly and waiting for him to finish. "What is it, Ricardo?" he asked.

"I think I know someone in San Cristobal who could help," Ricardo said. He went to the window overlooking the square. "See that Indian there-the one sitting on the bench near the corner?"

Ken and Sandy joined him.

"Sure, I see him," Ken said. "But what makes you think he could help? Do you know him?"

Ricardo shook his head. His eyes were bright. "I only wanted you to look at him. He is about my size, no? Perhaps he is a little darker than I am, but if my face was dirty I would look much like him-like an Indian who had a long, dusty walk to town from a farm in the hills."

"Wait a minute," Sandy said. "Are you saying you could disguise yourself as an Indian?"

"Why not?" Ricardo drew himself up proudly. "After all, I am part Indian. It would not be so difficult. And if I had a white wool serape like his, and a big straw hat, then I think we would look much alike. And I think no one would notice me then, if I walked around San Cristobal close to where you walk. But I would be watching. And I would see if anybody followed you-anybody who might be interested in the map in my amulet.”

Ken and Sandy looked into Ricardo's excited face, and then glanced at each other.

"Can you speak the Indian language?" Sandy asked. "If not, you'd give yourself away the first time anyone spoke to you."

"No, I do not speak the language of any of the Indians here," Ricardo admitted. "There are several languages in this region. But I think most Indian boys speak Spanish also. So no one would be surprised if I spoke in Spanish. I am sure it would be safe. And we can work out the exact way you will walk," he hurried on. "You will tell me just what streets you will take. Then I will not have to stay very close to you, and no one will guess what I am doing. You think it will work, no?'

Ken was nodding. "It's risky," he said. "But I think it might. Especially, as you say, if we plan ahead of time the direction Sandy and I will walk-"

"We won't even have to do that," Sandy broke in. "We've got three megabucks. Remember? Each of us can take one, and with them we can all be in constant communication! I think it would work, Ken!"

"But where can we get a white wool serape and the right kind of hat?" Ken asked.

"That is easy!" Ricardo announced. "When we drove from the airport I saw, near the market, several stores which sell such things. We could go and buy them now."

"Sure you could," Sandy said. "Go ahead, you two. And while you're buying Ricardo's disguise I'll be getting the megabucks ready."

Ken grinned. "You're forgetting something, aren't you?"

Sandy looked surprised. "What?"

"Food."

"Oh. That." Sandy grinned too. "No, I'm not forgetting it. I'm just postponing it for the common good." He glanced at his watch and then out the window once more. "We've only got a couple of hours of daylight left. Get moving.”

CHAPTER X

IDENTIFIED

When Ken and Ricardo returned to the room they found Sandy waiting for them impatiently.

"No wonder it took you so long," Sandy said, eying their purchases. "How many costumes did you buy, anyway?"

Each of the boys carried several items, some wrapped, some unwrapped.

"Only one full costume," Ken told him. "But we didn't think it was smart to buy just the things a Chamula wears, and nothing else, or to buy all the items of the costume in one store. It would be too easy for anybody who was interested in our movements to find out exactly what we'd done in that case."

"I guess you were right," Sandy agreed. "I hadn't thought of that. What's that word you used?" he added. "Cham-what?"

"Chamula," Ricardo told him. "There are many different tribes living in this region, you see, and each one has its own kind of costume. It is the Chamulas who wear the white scrape."

As they spoke, the boys were laying their purchases out on one of the beds, sorting them into two piles. In one pile was a gaily embroidered blouse, several woven belts in bright colors, a long, dark-blue rebozo and a shorter one of magenta wool. "Maybe Mom can use some of these things," Ken murmured. "O.K. Ricardo. Everything in the other pile is yours."

"And now, my friends," Ricardo announced, "I will show you a great magical trick. I will change into a Chamula Indian before your very eyes."

Sandy grinned at the enthusiasm with which Ricardo was tackling the role he had chosen for himself. "I don't care whether you do it before my eyes or behind my back, but do it fast. We don't have much daylight left."

"This will not take long," Ricardo assured him.

A moment later he had pulled on white pants that reached to just below his knees, and topped them with a loose, roughly made white shirt. "Now a little mud, Ken," he said, as he stooped to strap a pair of handmade leather sandals on his bare feet.

"One order of mud coming right up." Ken took an old envelope out of his pocket and dumped its contents into a water glass. "Instant mud," he told Sandy. "A new invention Ricardo and I have just developed. You start with a rare ingredient we mined in the patio here. Then you just add water"-he stepped into the bathroom long enough to fill the glass-"and stir. You now have," he concluded, mixing the contents of the glass with his finger, "a mud mix which even an expert could not tell from the genuine article normally obtainable only in the rainy season."

Sandy grinned in spite of his impatience. "Remarkable invention," he applauded. "I was wondering how we were going to get around the fact that Ricardo would be a too-new looking Chamula." He helped Ken and Ricardo smear the muddy liquid over the Mexican's bare feet and legs. They rubbed some on his arms too, and on his face and neck.

"When this dries," Ricardo said, with satisfaction, "anyone who sees me will think I have walked a long way to town over very dusty roads."

"Your clothes still look too new," Sandy objected. "And we've used up all the instant mud."

"We have more," Ken corrected him. He reached into his pocket and brought out a second envelope full of earth. "It's a good thing I have a habit of carrying old letters around with me," he said. "Here, just get your hands good and dirty in this, and then rub them over Ricardo's pants and shirt. I'll go to work on the scrape."

He spread the white woolen rectangle on the floor. "It's too bad to mess up this hand-woven wool," he said, "but duty is duty."

The earth he rubbed into the creamy garment adhered quickly to the fuzzy surface. In less than a minute the scrape looked streaked, soiled, and well worn.

"That is enough, I think." A grimy Ricardo took the scrape, pushed his head through the slit at its center, and then pulled the wool down so that it covered his body back and front.

"Here's the belt," Ken said, handing him a length of thick leather with a heavy buckle at one end and holes punched at the other.

Ricardo put the belt around his middle and pulled it tight, so that the free-hanging lengths of white wool hugged his body.

"And now the hat," Ricardo said, going toward the bed.

Sandy eyed the plain white straw with a high crown and a wide brim that curled up slightly on die sides.

"You could have done better than that," he said. "Why didn't you get one of the hats with the long ribbon streamers?"

"Your ignorance amazes me," Ken told him. "A Huixteco Indian might wear such a hat. A Zinacanteco might wear such a hat. But have you ever seen a Chamula wearing a hat with long ribbons?"

"How fortunate I am," Sandy told him, grinning, "to be acquainted with that great anthropologist, Ken Holt."

Then Ricardo was standing in front of them, his hat pulled forward so that it shaded his face.

"It really is a great trick, Ricardo," Sandy said admiringly.

"I could pass you on the street and not recognize you," Ken assured him.

"Not bad, no?" Ricardo grinned at himself in the mirror.

"Now let's see if we can put the megabucks where they won't show," Sandy said. "Here's yours, Ricardo."

"I could hide three or four of these," Ricardo assured him. He slipped the small transceiver inside his woolen garment, letting it come to rest against the belt. Then he plugged the earphone wire in place, ran the wire up through the head slit of the garment, and put the earphone itself in place in his right ear.

Sandy already had his own transceiver in his shirt pocket under his jacket, and had threaded the phone wire out past his collar to the tiny plug in his ear. Ken followed his example.

Sandy checked to make sure all the sets were turned on.

"All right," he said then. "Let's try them out." He walked to the farthest corner of the room, turned his head down slightly in the direction of the tiny transmitter in his pocket, and whispered a few words.

"Coming in fine," Ricardo assured him.

Ken had heard the whisper with equal clarity through his own earphone.

"Now you try, Ricardo," Sandy said.

Ricardo bent his head, directing his voice down through the wool that covered his instrument. Both the others picked up his quietly whispered words.

"We're all set then," Sandy said. "I figured you could slip out of the hotel through that door at the end of the corridor, Ricardo," he went on. "We'll make sure the hall is empty first, so that no one sees you leave here. Then if you walk over into the square, and sit down on a bench-let's make it that same bench you pointed out to us before, when you showed us the Indian-Ken and I will walk out through the front door and stroll past you. Let us get a couple of hundred feet beyond you, and then get up and walk after us. We'll walk slowly, and stop to look into a lot of shop windows. That will give you a better chance to see if somebody is trailing us."

"Don't take any chances, Ricardo," Ken warned soberly. "If we're right in our suspicions that the same men who have been after you before are now here in San Cristobal, you've got to be careful. Those men have already seen you several times, so don't get too close to them."

"Keep the megabuck going all the time," Sandy said. "Just keep talking into it. Then we'll know you're all right. And if by any chance you think somebody has tumbled to your disguise, let us know right off-and we'll turn around and get right back to you."

'I will be careful," Ricardo assured them.

"We're set then?" Ken asked. The others nodded and he stepped to the door and opened it. He glanced casually out into the corridor, saw no one, and put his head out to look up and down the length of the hall. After a moment he said quietly, "O.K."

Ricardo slipped past him and moved away toward the door at the corner of the building. Ken waited until he was outside before he motioned to Sandy.

They left their key at the desk and strolled out into the street.

"I see you." The voice sounded so loudly in both their ears that they jumped.

Sandy recovered first. He bent his head toward his concealed transmitter and whispered, "You're coming in fine, Ricardo. But not so loud. You'll blow our heads off."

"Sorry." Ricardo had modulated his volume. "This is better?"

"Much better," Sandy assured him in a whisper. "I gather you can hear us all right."

"Yes. I am walking toward that bench," he added a moment later. "I cannot see you because my back is to the hotel. Can you see me?"

Ken and Sandy were walking across the street into the big plaza. It was a kaleidoscope of color in the late light Vivid flowers bloomed in the flower beds. Strolling figures wore gay dresses and sports clothes of the kind Ken and Sandy were familiar with at home, or the Indian costumes that were already becoming familiar to them in San Cristobal de las Casas. There were many Chamulas among them, all dressed in the same kind of white garments Ricardo had put on a few minutes before in the hotel room.

Ken and Sandy looked at each other and shook their heads. Ken spoke their decision into his transmitter.

"We can probably see you. We're probably looking right at you, Ricardo. But so far we can't tell one Chamula from another."

The faint sound that reached their ears was, Ken thought, Ricardo's self-congratulatory laugh.

"Scratch your ear," Sandy advised into his transmitter.

And almost immediately one of the figures in white wool and broad white hat reached a hand up to his ear and scratched it thoroughly.

"O.K.," Sandy said. "We saw you. You're near the bench. You're sitting down on it now."

"That is right." Ricardo's whisper traveled across the plaza.

"We'll walk right past you," Sandy told him a moment later.

He and Ken moved slowly, as so many of the others in the square were doing. They looked with a tourist's curiosity at the flowers, at the Indian costumes, at the bandstand in the center of the plaza. Once they tilted their heads up to see the top of a towering church. They pointed out to each other certain interesting shops among the buildings edging the square. They never looked directly at Ricardo, but they were always aware of his slight figure, sitting placidly on the bench.

They were still some distance away from him when their earphones came alive.

"Two men are walking after you," Ricardo was saying. "They were sitting on a bench opposite the hotel entrance when I came out. Perhaps you saw them too. They got up soon after you passed them, and started in the same direction you are taking."

"Easy," Ken warned him. "There are lots of people in the square. Maybe these two just happen to be taking the same path through the square we're on. Well walk over to the bandstand now. See what they do then."

He and Sandy turned out of the main path into another one that ran toward the empty bandstand. They stood before the little structure for a moment, in apparent admiration of the workmanship. Then they turned and walked back toward the main path they had been on earlier.

Ricardo's report came in just as they turned.

"The two men didn't follow you to the bandstand," he said, as if whispering close beside them. "But they stopped on the path, as if they were so interested in what they were saying that they forgot to walk on. Then when you started back this way they began walking again."

"Can you describe them?" Ken asked into his transmitter.

"Not yet," Ricardo said. "They are not yet close enough. But both are wearing white Panama hats. If you walk past me, and they follow you, I will be able to get a good look at them."

"We're going to do that," Sandy told him. "But don't look up at us when we come by. We won't look at you, either."

A minute later Ken and Sandy were moving slowly past the bench on which Ricardo sat, his head forward so that his chin rested on his chest. The big hat covered his face so well that only the tip of his chin was visible. A casual passer-by, Ken felt sure, would have taken him for a young Indian boy from the country, worn out by a long day in town.

Ken spoke quietly into his microphone when they were a dozen steps beyond him. "Be careful not to stare too openly at those men. We're going to turn left when we reach the far edge of the square," he added, "and walk around the outer rim of it.'

"If they are still following you when you turn," Ricardo whispered, "I will come after them."

They reached the edge of the square and turned left, to stroll along its edge.

"They have passed me," Ricardo's voice said into their ears. "They are both about the same size as Ken. One wears a dark-brown suit. He called the other man Adalco, just as they walked past me. The other-Adalco-wears light-blue slacks and a tan jacket. He has a mustache and glasses with wide, dark earpieces."

"Good work," Ken whispered. "We're going to cross the street now and look in the window of that bookstore."

As he spoke he gestured toward the store, and said aloud to Sandy, "Let's take a look at that shop."

The next time Ricardo's voice came to them they were only halfway across the street. "They turned to walk behind you around the edge of the plaza," he reported. "They are about a hundred feet behind you now. And now I am following them. I am the same distance behind them."

"Don't come after them any farther," Ken advised. "Sit down on the nearest bench. After we look in this window we'll backtrack past you again and give you another look-if they're still following us."

"All right," Ricardo agreed. Then he added, "They have stopped walking. They see you standing in front of the bookstore. They are just standing and talking, as they did before."

Ken and Sandy loitered before the bookshop window for several minutes. They pointed out interesting titles to each other, and practiced reading some of the Spanish words aloud.

Once, with a faint laugh, Ricardo corrected Ken's pronunciation. "They are still standing there, waiting for you to move," he said.

Finally Ken and Sandy turned away from the window, and crossed the street again back into the square. They had to side-step to avoid bumping into two men of medium height, one wearing dark brown, the other blue slacks and a tan jacket, both in wide-brimmed Panama hats that shaded their faces. The men were talking in rapid Spanish as the boys passed them, and seemed so engrossed in their conversation that they did not appear to notice the fact that Ken and Sandy had to move around them.

A Chamula on a bench not far away was scratching his ear. Ken and Sandy strolled past him. A dozen paces farther on, Ken said casually, aloud, "Remember that night in my father's apartment, Sandy?"

Ricardo caught the allusion through the transmitter. "Is that what you think too?" he asked eagerly. "That these two men have the same build of those two men?"

"That's the way they looked to me," Ken whispered into his transmitter. At the same time he eyed Sandy.

Sandy nodded soberly.

"They are moving again now," Ricardo reported almost instantly. "Once more they are following you."

"All right," Sandy said significantly. "I've had enough. Let's get back to our room."

"I guess we are both convinced now, Sandy-no?" Ricardo said into their ears. "I guess we must admit that Ken was right all along."

"I guess so," Sandy agreed quietly.

CHAPTER XI

CONVINCING PERFORMANCE

Ten minutes later, back in their room, Ricardo added one more piece of information to what they had learned. Before slipping into the Altamira through the corridor door, he had watched the two men enter the Hotel Mexico, on the opposite side of the plaza.

"You saw the place," he reminded them, as he pulled the white wool scrape off over his head. "It has a restaurant facing the street."

"I noticed it," Ken said. "So now we know where they're staying-good work, Ricardo. The more we know, the better we'll be able to plan our next step."

"For me," Ricardo said, grinning, "the next step is a shower with much soap."

"We all need showers," Ken agreed. "But you'd better take the first one, Ricardo. If the Altamira's supply of hot water happens to be limited, you ought to have a chance at it before it runs out."

"Our first job," Sandy muttered, as Ricardo disappeared, "will be to make a phony copy of the amulet map. Somewhere in my bag I've got a couple of Brentwood Advance letterheads. We'd better use one of them-don't you think? That will give the impression that we copied the map even before we left home."

"Good idea," Ken agreed.

"There seems to be plenty of hot water left," Ricardo announced when he emerged from the bathroom.

"Good!" Ken said. "Let's get cleaned up and have dinner before we really settle down to work."

"Hmm?" Sandy glanced over at him vaguely.

"I said let's get ready to eat," Ken told him.

"Oh." Sandy looked surprised. Then he grinned. "What a good idea! Why didn't I think of it myself?"

They were back in their room before ten, after a meal that had concluded with the Spanish caramel custard for which, Sandy always insisted, it was worth traveling to Mexico. At Ken's suggestion they asked the waiter to bring their coffee to their room. "A large pot of it," he'd said. "Enough for several cups each."

"This will help keep us awake," he said, when the waiter had left. "We've got a lot to do."

"And this will help keep us from freezing to death," Sandy said, moving toward the little fireplace in one corner of the room.

There was a good supply of wood stacked on the hearth, and several tiny bundles of resin-rich splinters to be used as kindling.

"Ramon told us it would be cold down here after dark," Sandy added, as the first yellow flames shot up the chimney. "But I didn't believe it would be this cold."

The coffee was long gone, and almost all the wood had burned to ashes, by the time they finally finished the various chores they had set themselves.

Ken rubbed the back of his neck and spoke around a half-stifled yawn. "Well," he said, "I guess that does it."

Faintly, through the wooden shutters closed over their windows, and the heavy drapes drawn across them, they could hear a church bell solemnly tolling the hour of two.

Sandy rolled his shoulders to ease aching muscles, and then got up to put the last log on the dying fire.

"I guess it does," he said.

The fake map was complete, well creased and slightly soiled along the edges, as if it had been much handled. They had agreed that the odds were overwhelmingly in favor of the tunnel entrance being somewhere inside the hacienda enclosure, and Sandy had therefore shifted the location of the dots only slightly. Working from the scale of the amulet map, he had calculated the distance and direction that would move the indicated tunnel entrance only one hundred feet northwest of its original position. He had also indicated the treasure as being in the extreme end of the tunnel, at the spot where the plumed serpent was drawn on the original map. A tiny drawing of a plumed serpent occupied the place marked tesoro on Ricardo's map.

Ken and Ricardo had spent much of the evening studying the large-scale police map. On it they had noted several places that might be used as hideouts for themselves, after they had checked out of their hotel and pretended to leave San Cristobal. They had also selected two elevated spots which they hoped would prove to be good observation posts from which to watch what went on inside the hacienda enclosure.

Ken had also written a long letter to Ramon, describing their day's activities and what they planned to do. The letter ended with a promise to write or phone the police officer within another day or two, to report the progress of their venture.

All three of them had co-operated on devising a method for letting the map Sandy had laboriously made fall into the hands of the two men who had trailed Ken and Sandy around the square. And they had rehearsed a conversation Ken and Sandy hoped to be able to conduct within the men's hearing.

Their final chore had been to figure out in detail exactly what they would do in the morning when they drove out to the hacienda to set in motion their scheme for outwitting the man called Adalco and his companion.

Ken's little traveling alarm clock roused them at eight o'clock. Sleepily they stumbled around the room, getting in each other's way as they dressed. But a hearty breakfast brought them wide awake, and when they were ready to leave the hotel at nine o'clock they were eager for their first sight of the two men Ricardo had seen entering the Hotel Mexico the night before.

"There they are," Sandy said quietly, with his hand on the door of their small, rented car. "Across the plaza, in front of the Hotel Mexico."

A few moments later, as they drove out of the plaza in the direction of the hacienda, Ricardo turned around from the rear window through which he had been looking. "They got into a green station wagon," he reported.

"Good!" Ken said. "That's one more thing we know about them: they drive a green station wagon. Don't go too fast," he warned Sandy. "Or too slow, either. We've got to look as if we had no idea we were being followed."

"But we are!" Ricardo said with satisfaction a moment afterward. "Here they come-they just turned out of the square onto this street."

Several times, as their small car climbed and dipped and twisted its way along the dusty road to the hacienda, they caught glimpses of a green station wagon behind them.

Sandy made no attempt to conceal their own car when they reached the place where they had left it the day before. He simply pulled it off the road into the dry grass. Then, together, they once more started their way on foot up the steep grade toward the crumbling walls towering above them.

They were halfway up the hill when the green station wagon drove past below, not pausing as it passed the boys' car.

"Let's not waste time now," Ken said, as they went on up the hill. "We've got to check on those observation posts we lined up last night. We want to make sure they're high enough above the hacienda to give us a good view of the place."

"But we don't want to have that police map spread out so that they can recognize it, in case they're using binoculars," Sandy said. "When they get back here I suppose they'll sneak up to the top of the stairs in the church-to the same place where we found those cigarettes yesterday."

"I suppose so," Ken agreed.

"I could go up there right now," Ricardo offered, as they neared the gateway, "and when I see them coming I could warn you through the megabuck in time for you to put the map away."

"Good idea," Ken said. "They'll probably climb the hill on the north side of the enclosure, and come through that hole at the back of the church- the way one of them apparently left yesterday. So don't wait too long to abandon your position."

Once inside the walls they all turned on their mega-bucks, and then Ricardo hurried off toward the church while Ken and Sandy went toward the ruins of the Obregon house. There they spread out their large-scale map of the region.

"See?" Ken said. "Here are the two hills we thought ought to make good observation posts." He pointed them out on the map. One rose some half a mile north of the enclosure, the other a slightly shorter distance to the south.

"There! That's the one to the north." Ken indicated it through the trees.

They located the other too, after climbing on a pile of rubble to give themselves a better vantage point.

"They'll both do," Sandy said. "From either one of them we ought to be able to see pretty clearly right down here into the enclosure."

"They may not be easy to get to, on foot through the undergrowth," Ken pointed out. "But we can't have everything."

Just then Ricardo's excited voice crackled in their ears. "They are coming up the hill toward the big hole in the church wall," he reported. "I think they will reach the hole in five minutes."

"O.K. We're finished here, anyway," Ken told him. "Come on down and join us, so we'll be ready to go into our act." He put the map into his pocket.

Sandy, in the same moment, took out the fake copy of the amulet map which he had made the night before. And they both pulled from their pockets their measuring tapes and compasses.

For a full hour, after Ricardo joined them, they solemnly went through the motions of making a survey of the interior of the enclosure. They handed back and forth the map Sandy had made. They referred to it constantly. They used their compasses and their measuring tapes. They argued. They climbed piles of rubble, sighted from the top, and then climbed down again to argue some more.

Finally Ken rounded up Sandy and Ricardo with a sweep of his arm. "Time for phase two of our operation," he said under his breath as they joined him. Then he raised his voice and added, "I'm sorry, Ricardo, but this map is simply no good at all!"

"I agree," Sandy said, nodding vigorously. "The thing is absolutely worthless. We just can't get a fix from it. We have no idea where to start digging."

Ricardo picked up his cue and launched into the argument they had rehearsed the night before. He pleaded with Ken and Sandy to study the map a little longer.

Ken and Sandy answered him in turn. At each exchange their voices rose higher, their angry gestures became angrier.

Finally Sandy shouted, "Oh, give it up, Ricardo! Can't you see when you're licked? I'm fed up with the whole business!" And he turned and made his way swiftly toward the gateway. "You two coming?" he called back over his shoulder.

Ken hastened after him, beckoning Ricardo to follow.

Ricardo refused at first. Stubbornly he stood in the center of the enclosure, gazing around at the piles of rubble. Then he dashed after the boys, catching up with them when they were halfway down the slope toward the car.

Sandy got behind the wheel, turned the car in a cloud of dust, and headed it back toward town at a faster pace than they had ever attempted on that rough road.

"Whew!" Ken said, slumping back against the seat. "I think we all gave a great performance. If we didn't look like three people disgustedly giving up the chance to find hidden treasure, I'll eat my hat."

Back at their hotel, they lost no time carrying out the next operation they had planned. While Ricardo changed into his Chamula costume, and Sandy tossed clothes into their bags, Ken went out to the desk and told the manager they were leaving.

The man was understandably surprised, and begged Ken to tell him if there was anything wrong with their room, or with the meals they had been served.

"No, nothing," Ken said shortly. Thanks," he added belatedly. "It's just that-well, we've changed our minds, that's all. Your check-out time is three o'clock, isn't it?"

"That is so, Senor Holt. But-"

Ken didn't let him finish. "Good," he said. "Well, we'll have all our luggage out of the room long before then. And now, if you'll just give me our bill, I'll get that paid right away."

Fifteen minutes later, after Ricardo had slipped out of the hotel by way of the door at the end of the corridor, Ken and Sandy marched out through the lobby to walk across the plaza. The megabucks were operating.

They pretended to take an interest in everything around them, but they were heading directly for the Hotel Mexico.

"There's Ricardo," Ken said quietly.

Ricardo was sitting on a bench directly in front of the glass-fronted restaurant of the Hotel Mexico. He was slowly eating a rolled tortilla he had purchased from a passing street vendor, and staring into space as if he had nothing on his mind but the rhythmic moving of his jaws.

Ricardo's voice sounded through the tiny receivers in their ears. "Our friends were sitting on a bench within sight of the Altamira when I first came out here. As soon as they saw you, they got up and began to stroll around. They are now following you, at a distance of about fifty feet."

"Check," Ken said softly into his transmitter. "There are two empty booths in the Hotel Mexico restaurant right in front of that big window. We'll head for one of them. Sure you'll be able to see us in there-and anybody who sits down in the next booth?"

"Don't worry," Ricardo's voice assured them. "When I finish this tortilla I will pretend to go to sleep at the foot of that lamppost facing the window. I will see everything."

Ken and Sandy walked directly past Ricardo on their way into the restaurant. After a moment of seeming indecision, they chose one of the empty booths Ken had noticed from outside. Sandy slid first into one of its high-backed benches, to sit with his shoulder almost touching the window. Ken sat down beside him. They both picked up menus, and pretended to study them.

Out of the corner of their eyes they watched Ricardo swallow the last of his tortilla, squirm around on his seat as if trying to get comfortable, and then move to the spot he had chosen at the foot of the lamppost. There, scarcely twenty feet beyond the window, he sat down on the sidewalk, crossed his arms upon his drawn-up knees, and appeared to go to sleep with his head on his arms.

While Ricardo was apparently settling down for his informal siesta, the man named Adalco and his companion crossed the street toward the hotel and entered its restaurant. Like Ken and Sandy, they paused inside the door as if to make up their minds where to sit. Then, as if on impulse, they walked across the room and slid into the booth at the boys' backs.

The restaurant waiter came over to ask what the boys wanted.

"I don't care what I eat," Sandy said, in an angry voice. "Bring me-oh, an order of eggs rancheros. Huevos rancheros," he corrected himself.

"The same for me, please," Ken said. "And coffee."

"I’ll have coffee too," Sandy agreed.

"Si, senores. Doshuevos rancheros, dos cafes" the waiter murmured.

The men at the next booth apparently signaled to him as he turned away, because the boys could hear them giving their order immediately.

Sandy spoke the first sentence of their planned dialogue before the waiter started toward the kitchen.

"Some town this is!" he said disgustedly. "You freeze at night and roast all day. Here, get rid of this for me, will you, Ken?" He slid out of his jacket as he spoke. Ken slipped his earphone off and tucked it out of sight beneath his coat collar before he rose to hang Sandy's jacket on the hook set into the post above the partition between the two booths.

As he lifted the jacket to the hook, he let it brush against the man seated just below it on the other side of the partition.

"I beg your pardon," Ken said.

"It is nothing," the man said politely. He glanced up at Ken as he spoke, and the thin mouth beneath the neat mustache smiled.

Ken managed to smile back, but the muscles in his stomach tightened at this first face-to-face encounter. He had to make an effort, when he sat down again, to pick up Sandy's lead.

"Well, you won't have to be complaining about San Cristobal much longer," he said. "We'll be in Mexico City in time for dinner." He inserted the earphone into his ear as he spoke.

"We never should have let Ricardo persuade us to come down here in the first place," Sandy said, his voice still sounding angry.

"Maybe not," Ken said. "But, after all, we did agree to come. You didn't have to talk to him the way you did-so that he wouldn't even come out to eat lunch with us. After today, we'll probably never see him again," he went on. "When he gets back to Rio Claro tonight, he may never leave it-and we may never get to Rio Claro."

"I hope not," Sandy said brusquely. "I've had enough of Ricardo Montez and his map."

"I still think we may have been too hasty this morning," Ken said after a moment. "I'm going to take one last look at the map. Let me see it, will you?"

"It's in my coat pocket," Sandy snapped. "Get it out if you want to. But I've finished trying to make sense of it."

Ken reached around without standing, and fumbled in Sandy's pocket for a moment. Then he spread out the faked map.

"There must be some way of figuring out where this tunnel entrance is," Ken mused, half to himself.

As he spoke, Ricardo's voice sounded faintly in his ear. "They are leaning back against their bench, trying to hear you," it said.

"Suppose we sighted from the gateway to-" Ken went on. "No," he said quickly. "That wouldn't accomplish anything."

"Give it up, Ken," Sandy said. "Here comes our food. Let's eat and be on our way. We haven't got too much time if we want to get to Tuxtla Gutierrez and catch that plane. Unless you want to spend another night here and get a plane tomorrow."

"All right," Ken said, with a show of reluctance. He twisted around and stuffed the map back into the inner pocket of Sandy's coat. When he sat down he tackled the plate of sauce-covered eggs the waiter had put at his place.

They ate in silence for a few moments. And then Ricardo's voice spoke in their ears. "The man with the mustache is reaching into Sandy's coat pocket!" it breathed. "He is taking the map!"

CHAPTER XII

INTERRUPTED PICNIC

"Come into my parlor, said the spider to the fly." Ken barely breathed the words, but he was glad the men at his back could not see the triumphant smile he wasn't able to repress.

Ricardo's voice whispered in their ears. "They have the map spread out on the table. They are putting another thin piece of paper on top of it. They are tracing the map I"

It was difficult to carry on a conversation over Ricardo's voice, but they didn't dare let a silence last too long for fear the men at their backs would become suspicious. Somehow, they kept the talk going as the minutes ticked by.

Finally, through the tiny receivers, they heard the words they had been waiting for. "They're folding up the map," Ricardo reported. "They're putting it back into Sandy's pocket! It's done!"

Almost immediately the men behind them called for the waiter and asked for their bill. Five minutes later the boys heard the welcome sound of feet scraping across the floor as the men got up to leave.

Ricardo saw them go. He seemed to rouse himself slowly from a nap, rubbing his eyes. Then he stood up, looked vaguely around the plaza, and began to saunter across the big open square toward the Altamira. He was in their room and already out of his Chamula costume by the time the boys joined him there.

"So far so good," Ken said. I'm sure they heard us say we were leaving, but they'll probably check up on us. So let's keep an eye out for them on our way to Tuxtla Gutierrez."

They caught one glimpse of the green station wagon as their own little car was traveling back and forth in the hairpin turns that took them down the first long drop out of San Cristobal. They caught a second glimpse of it as they parked their car at the Tuxtla Gutierrez airport. The station wagon came to a stop at the far end of the parking area, waited until the boys were carrying their bags toward the administration building, and then wheeled around and headed back toward San Cristobal de las Casas.

"Well, that's that," Sandy said with satisfaction. "We can start heading back ourselves now." He looked at Ken. "You still think we have to struggle back along that unpaved mountain road all the way to San Cristobal?"

"It's the only safe thing to do," Ken said. "Suppose they have a flat tire, or stop at a roadside cafe-and see us driving past?"

"You're right," Sandy agreed reluctantly. "O.K. Let's go into town and buy our camping supplies."

By five o'clock they were heading out of Tuxtla Gutierrez, the little car loaded down with sleeping bags, a small camp stove, and an assortment of food that was ready to eat or could be easily prepared.

Ken had to shift into low gear at the bottom of the first long climb. "If the road is as bad as this all the way, it'll take us three times as long to get to San Cristobal as it took us to get here."

They completed roughly half their journey that night, pulled off the road near a stream, ate a simple meal, and went to sleep early in the cozy warmth of their sleeping bags. They were moving again by five the next morning, pushing the little car to its limit to make time.

Finally they were bumping their way over the single, cobblestoned street of a village near the hacienda. Ken had been holding the road map while Sandy drove. "We take the first road on our right once we're through this village," he warned. "And from then on," he continued, "we'll have to be very careful. Once we make that turn, we'll be pretty close to those two hills we're going to use as observation posts."

Ken spotted both the hills half a mile after they found the road beyond the village. He pointed them out to the others and added, "I'd say we're close enough-anywhere along in here. Let's leave the car in the first likely place we find."

A thousand feet farther on, Sandy found an opening in the pine trees thickly bordering the road. He eased the car through it, and drove over a bough-shaded carpet of brown needles until he came to a small clearing. "How about this?" he asked.

"Made to our order," Ken said. "And now let's get up to those hilltops."

"But not until we've packed some food to take along," Sandy insisted. "We may be up there until dark."

They were ready to leave half an hour afterward. In one of the woven string bags they had purchased at a village market, Ricardo had a pair of binoculars, his transceiver, a compass, several hard-boiled eggs, two rolls, and a canteen of water. Sandy and Ken had similar rations and identical equipment in their own string bag, except that they intended to share a pair of binoculars. Ricardo was wearing his Chamula costume, in case it proved necessary for him to leave his observation post to reconnoiter.

"O.K.," Ken said. "Don't forget to keep in touch, Ricardo."

"I will," Ricardo promised, and set off cross-country toward the more northern of the two observation posts they had chosen the day before. The boys waved to him, and moved in a slightly different direction toward the second hill that stood to the south of the hacienda enclosure.

They made better time than they had hoped. The pines through which they walked stood tall and straight, and the ground beneath them was free of underbrush. Ricardo made even faster progress. Ken and Sandy were barely at the foot of the slope they had to climb when Ricardo's voice reported that he had reached the summit he had been aiming for.

"I will let you know as soon as I can see down into the enclosure," he added. "Where I am now, there are too many trees."

Fifteen minutes later they were eagerly reporting back and forth. Ricardo had found the vantage point he was seeking. The boys had found one equally good. The three observers agreed that they would be certain to see two men walking around inside the walls.

"But I don't see a soul," Ken concluded. "Maybe they-" He caught his breath and said swiftly into his transmitter, "There's a cloud of dust moving along the road toward the place where we parked yesterday and the day before-the place at the foot of the hill!"

"I see it!" Ricardo told them excitedly.

A moment later the green station wagon was clearly visible as it drew off the road. Then the car's front doors opened, on either side, and two figures emerged. They both moved to the rear of the car, where they took out two shovels, a crowbar, and a wicker basket. Then, moving slowly under their burdens, the two men climbed the steep grade that led to the west gateway of the enclosure.

When the men moved through the wide open gateway, Sandy spoke into his transmitter. There was a laugh in his voice. "Watch closely, gentlemen," he said. "We are about to learn exactly where the tunnels are not."

The two men were not always visible, as they moved rapidly back and forth among the trees and the vine-tangled brush. The expressions on their faces were completely indistinguishable at the distance of a third of a mile, even through high-powered glasses. But the purpose and plan of what they were doing was perfectly clear. Starting at the church, they surveyed a line across the rubble-strewn enclosure to a point roughly opposite the gateway, and there they drove a stake into the ground.

"Did you see that?" Ricardo's breathless voice sounded in the boys' ears.

"We saw," Ken assured him.

"And now we know," Sandy said. "Exactly one hundred feet southeast of that stake is where the tunnel entrance really is!"

"It is so exciting-no?" Ricardo said.

"It's exciting all right," Ken told Ricardo, across the space that separated them. "But we'd better try to take it easy. Now they'll start digging-and we may be here for hours before they give up."

The men cleared sprawling vines away from the spot where their stake stood, and then began to dig down into the hard earth.

The mounting sun grew hotter. Ken and Sandy moved their position several times, in an effort to keep in the shade. Ricardo reported that he had pulled off his woolen scrape. The men were still digging. They kept steadily at their back-breaking job until they had made a hole some six feet square and so deep that when they stood inside it they were concealed from the hips down. Then at last they stopped, climbed out of the hole, and disappeared from sight for a time beneath a shady tree.

"Now what?" Ken wondered aloud.

His question was answered ten minutes later. The men came into sight again and cleared a new patch of ground, a few feet to the west of where they had originally dug. There, once more, they attacked the earth with crowbar and shovels.

When the sun was high overhead, the boys pulled their food and canteens from their bags and ate, taking turns at maintaining their vigil. The men had apparently brought no food with them. But they paused more and more often, as time went by, to drink from straw-covered bottles they brought forth from their wicker basket.

The second hole, roughly similar in size to the first, was abandoned as the boys finished their frugal meal.

Once more, then, the men disappeared into the shade of a tree. That time they remained out of sight for a longer time.

"Do you think they might have left-and we missed them?" Sandy had scarcely asked the question when the men came into sight again.

For the third time they cleared a patch of ground and attacked it with their tools.

At three o'clock they climbed slowly out of the third hole they had dug. For several minutes then they stood at its edge, their hands and arms moving in what were clearly angry gestures.

"Perhaps now they will give up?" Ricardo suggested hopefully.

"Not yet," Ken answered a moment later. "There they go again."

The weariness of the two men was apparent now in every move they made. Their tools no longer moved rapidly down, up, and down again. Their bent backs straightened oftener, and with obvious effort. They were only knee-deep in their fourth hole when suddenly one shovel was hurled to the ground.

A moment later the man who had wielded it climbed out of the hole, picked up a jacket he had long ago tossed aside, grabbed the wicker basket, and started toward the gateway.

The other figure remained motionless in the hole for perhaps half a minute. Then it too climbed out and moved toward the gate. Neither figure paused. Neither turned back even briefly toward the mounds of earth, stone, and adobe that had been so laborously piled up.

The boys all forced themselves to remain where they were until the green station wagon disappeared toward San Cristobal in a cloud of dust.

"All right," Ken said finally. "Let's go. We'll meet you at the car, Ricardo."

Ricardo was at the car ahead of them, impatient to move on to the next step of the plan they had worked out the previous night-a plan that, so far, had worked perfectly.

Sandy took the wheel and Ken guided him by following the large-scale map of the region. By tiny roads which obviously seldom saw a car, they made their way toward San Cristobal, approaching it from the northeast rather than from the southwest as the main route did.

"I think we're being overcautious," Sandy complained, as the wheels jounced in deep wagon ruts. "We've covered our tracks. They can't possibly suspect that we're still around here."

"Let's hope they don't," Ken said. "But let's not get careless now-when we've gone to so much trouble so far."

"Trouble is right," Sandy muttered. "Hard-boiled eggs, hard rolls, and plain water for lunch!"

"I will try to buy some chorizos while I am in San Cristobal," Ricardo assured him. "They are Spanish sausage, you know-very good with rice. I can cook them over our fire tonight."

At a spot they had previously marked on the map, a scant mile outside of San Cristobal, Sandy stopped the car in the dusk and Ricardo got out.

"We'll pull the car off into the grass and wait right here," Sandy told Ricardo. "But if you let us know the coast is clear, we'll drive toward town and pick you up on your way back. Don't forget that sausage. And be careful," he added.

Ricardo's voice came to them over their transceivers some twenty minutes later. They sighed with relief when they heard it.

"I am approaching the plaza," Ricardo reported. "Are you hearing me?"

"Fine," Ken told him. "Have you seen any signs of our friends yet?"

"Not yet," Ricardo reported. "And now I am going to take the earphone out of my ear. I may have to ask questions of someone, and it might be seen." There was a grin in his voice as he added, "I think not many Chamulas in this region wear hearing aids. I do not wish to be-how do you say it?-conspicuous."

Night fell swiftly over the little car parked at the edge of the road. Long silent minutes crawled past before Ricardo's voice spoke into their transceivers. "Ken-Sandy-it is all right!" he said. "They have left! They have gone to Mexico City!"

"You're sure?" Ken asked quickly.

"Very sure," Ricardo said. "The bellboy in the hotel told me."

"You asked him?" Ken said in amazement.

Sandy whistled. "You don't mind taking chances, do you, Ricardo?"

"It was not a big chance," Ricardo assured them. "I asked if Senor Adalco was in. If the bellboy had said yes, and went to his room to call him- well, then I would have run away very quickly. But he told me Senor Adalco and Senor Constanza checked out of the hotel to go to Mexico City on business. So then I asked if they will be back. I told him I wished to know if Senor Adalco will buy a small ancient statue I have shown him."

"And are they coming back?" Sandy wanted to know.

"The bellboy does not think so," Ricardo said. "They left no luggage. They did not ask for their room to be kept. And now I will buy chorizos and rice and we will soon celebrate with some very good food, made as my mother taught me."

"We'll meet you along the road," Sandy assured him. "We're starting toward town now."

They were at the edge of San Cristobal when their headlights picked up the white of Ricardo's serape. A moment later he was in the car and Sandy was turning around for the ride back to their campsite.

"I don't have to ask if you have the sausage," Sandy said. "I can smell it. And it smells absolutely great."

They drove at a good speed back to the spot where they had turned off the road the night before, and moments later their lights were illuminating neatly piled sleeping bags and the little stove, just as they had been left that morning.

"We will fry the sausage first," Ricardo was explaining, as Sandy lit the fire.

They had turned off their car headlights, for fear they would cast a glow against the sky that might arouse curiosity. The stove itself gave off a little light. When they needed more, momentarily, they used a flashlight.

"You know," Sandy said, as the aroma of frying sausage filled the air, "it occurs to me we could just as well have gone back to the hotel tonight-now that we know definitely our friends have departed from this region. But the smell of that sausage makes me glad I'm right here beside it. How much longer now, Ricardo?"

"Not long," Ricardo promised. "The sausage is done. I have added the rice. In half an hour, I think, it will be ready."

The voice that followed his spoke out of the darkness beyond the tiny circle of pale light. "A picnic in the woods!" it said. "How pleasant. Would there perhaps be enough extra food for two hungry men- men who spent a hard day digging?"

A flashlight beamed suddenly at them from the spot from which the voice had spoken. Almost instantly, from a few feet to its right, another beam flashed full on the boys, impaling them in a double brilliance. And in its glow, just beside one light, they could all see a revolver that was pointed directly at their seated figures.

CHAPTER XIII

FORCED LABOR

Before any of the boys could move, the same voice added, "You-don't try to throw anything." The words were accompanied by a flick of the gun toward Sandy. "It wouldn't do you any good this time. You wouldn't wake anybody up with the noise.

"Don't waste time, Adalco," the same voice continued. "That masquerading Indian isn't going to give you any trouble this time. Go and get it."

One of the lights moved away from the other. Circling slowly around behind Sandy and Ken, it came to rest behind Ricardo, pointing down at an angle over the shoulders of the white wool serape. The man who held the flash was visible to Ken now. He was the one who wore a thin mustache and glasses with dark earpieces.

Adalco's thin hand reached down over Ricardo's shoulder. "Let's have it," he ordered.

Ricardo hesitated. His eyes sought Ken's.

"Stubborn, eh?" Adalco's hand darted in a quick sideways motion, and Ricardo's head rocked from the blow.

Sandy's instinctive movement brought an instant warning from the man standing behind him with a gun. "Stay right where you are if you know what's good for you!"

Ken sensed the blind anger behind the men's words and their swift gestures. He felt that at this moment they would not hesitate to use a gun to silence any opposition they might meet. "Give it to him, Ricardo," he urged quietly.

Ricardo reached inside his shirt and serape, and started to withdraw the amulet on its chain.

"Hurry!" Adalco grasped the chain, and tugged at it roughly, snapping its thin links and pulling it free of Ricardo's neck with a skin-searing jerk. Then he stepped back a few paces and held his light on the amulet.

"Well?" the other man prodded after a moment.

"It cannot be opened with the fingers," Adalco said. "It will need a sharp knife edge." He began to fumble in his jacket pocket. "Keep that redhead covered, Constanza," he added as he pressed the knife blade against the rim of the silver disk. "Ah!" he said triumphantly, when it sprang open. He pried out the fragile map and unfolded it.

"Check it with the one we traced," Constanza said. "Use the lights on their car."

Adalco moved to the car by a route that never took him between the boys and the gun in Constanza's hand. He snapped on the headlights, and stood in their glow while he pulled a thin sheet of paper from his pocket and put it over Ricardo's map. Then he held the two maps, one over the other, against the glass of a light.

A moment later he said, "Of course we were right! They did just as we thought-they shifted the dots!"

Adalco took a second paper from his pocket. The brief glance Ken had of it told him that it was very much like the diagram of the walled enclosure which Gonzalez had sent them-a rectangle enclosing smaller rectangles and squares which represented the now-ruined buildings. Adalco held the amulet map over it, shifting it about until its position satisfied him. Then he found a small ruler in his pocket, and laid it in place.

"About thirty meters," he said finally. "Or probably exactly one hundred feet. We should have dug just that far southeast of where we did." As he refolded the maps, and put all three away in his pocket, he looked down scornfully at the boys. "So, we have at last the information you have tried so hard to prevent us from obtaining. I guess you were not quite as clever as you thought, eh?"

For the first long moment after the arrival of the two men in the clearing, Ken's mind had seemed numb from surprise and shock. But now he was trying to force himself to think, and to consider the position he, Sandy, and Ricardo found themselves in.

It was a dangerous position. There could be no doubt of that. The men had exposed themselves by committing a robbery unmasked, and knowing they had already been recognized. It was therefore highly unlikely that they would let the boys go free, and thus give them the chance to reach the police, until they themselves had made a safe getaway with whatever treasure they might find in the Obregon hacienda.

They had no right to that treasure. The methods they had used to obtain the map were proof enough of that. And if they made off with it, Ricardo would always feel that he had failed his trust. And Ken and Sandy would know that they were responsible for his failure.

The men were obviously determined and unscrupulous. They seemed heartlessly cruel as well, judging by that unnecessary blow against Ricardo's head. And they were both armed. Escaping them had seemed completely impossible until Adalco's last words.

But the arrogant smile that accompanied those words had told Ken something more about the men. A few moments earlier they had been blindly angry at the boys who had outwitted them. Now the tables were turned. Now the two men felt triumphant.

Playing up to their pride, Ken thought suddenly, might be the one way to make them relax their vigilance, and give Sandy, Ricardo, and himself the chance they needed.

He looked sideways at Sandy, a look that said, "Take it easy. Let's see what we can do with a little talk."

Then Ken looked up at Adalco and shrugged dispiritedly. "There's not much point in denying it, is there?" he said. "I guess we're not as clever as we thought. You've beaten us."

Constanza laughed. "Well, you are smart enough to understand that, at any rate. Now you will be ready to cooperate-and I think even with your limited intelligence you will see that what we expect of you is only fair. We did a lot of unnecessary work today because of your meddling. And so you will dig for us tonight-in the right place." He turned to his partner. "Get them ready to move."

Adalco cut several short lengths from the ball of heavy cord he took from his pocket. "You," he said, pointing to Sandy, "stand up and put your hands behind you."

The gun was less than three feet from Sandy's head. Slowly the big redhead obeyed. Adalco pushed him roughly so that he stood in the glow of the headlights, an easy target. Then Adalco bent down behind him, crossed one of Sandy's wrists over the other, and bound them tightly together.

He repeated the same process with Ricardo, and finally with Ken. When he was finished he put away the cord and took out his gun.

Constanza gestured authoritatively with his own weapon. "Now move. You know the way to the gate in the wall. Start walking. And don't forget we're right behind you, with two flashlights and two guns pointed where they will do the most good."

Stumbling clumsily, the boys moved out of the clearing, walked through the pine grove to the rutted trail, and turned eastward on it toward the ruins. After a quarter of a mile the trail ended in a clearing where charcoal burners had once worked. From there on, the boys had to make their way through a wood thick with undergrowth. Low branches, from which they could not protect themselves, lashed at their faces.

Ken could imagine how Sandy and Ricardo were faring. His own shoulder throbbed painfully from the blow it had received when he fell over a rock outcropping. The rope binding his wrists cut into them like hot wire. And the speed at which they were driven on, forced to balance themselves on the uneven terrain without the use of their arms, had them all breathless and exhausted by the time they finally reached the road that skirted the ruins.

"If you want us to be fit to do any digging, we will have to rest before we go on," Ken said.

Constanza gestured with his light. "Sit down! We will spare you five minutes. You will make it up by working harder."

The boys dropped down at the edge of the road, leaning back awkwardly on their bound wrists, trying to find some position that would let knotted muscles loosen.

Adalco laughed. "They look like three trussed-up fowls waiting for the butcher. And only a short time ago they were so proud of themselves!"

"We're not very proud now," Ken said, in what he hoped was a steady voice. "I suppose we'll never know where our plans went wrong," he added.

Adalco took the bait. "I am sure you could never figure it out," he said. "It was your car, of course. When we began to suspect that you had altered the map, we also began to suspect that you had not really left this neighborhood. So we checked with the garage in San Cristobal-and learned quite easily that you had not returned your rented car." He shrugged. "It was quite simple. You were careless. You were also stupid."

"I'll say we were," Sandy muttered disgustedly under his breath.

"You and your little trap with that map!" Constanza said scornfully "You should have realized that others can lay traps too-and more successful ones. We told the bellboy at the Hotel Mexico just what to say if anyone asked for us-and we made sure he would obey by threatening to complain about his service and getting him fired. Then when this little imitation Indian arrived"-he looked amusedly in Ricardo's direction-"it was simple enough to follow him. Once he got in your car, all we had to do was follow your trail of dust until you turned off the road, and then walk along in the tire tracks that led right to that clearing. To see you there, so prematurely rejoicing in your success -ah, that was a moment we shall not forget I"

"You have certainly known how to take advantage of our mistakes," Ken said glumly, as if in reluctant admiration.

"But your mistakes were so easy to take advantage of!” Adalco laughed. "And that is why we are going to get the treasure and you are going to get-"

"That will do, Adalco," Constanza said sharply. "You talk too much."

"But we're interested," Sandy said. "What are we going to get?"

"All that's coming to you," Constanza said. The amusement that had colored his voice briefly was now gone. He spoke the words in a cold, level voice that sent a chill down Ken's back.

Ken took a deep breath. His attempt to flatter the two men had earned a little information. He realized now that it would earn them nothing more. He determined to try another tack-to attempt to shake the men's obvious confidence in their own ability to outwit anyone who stood in their way.

"You've been lucky tonight," he said, looking up first at Adalco and then at Constanza. "A lot luckier than you were when you attempted to steal that amulet from Ricardo at his school, or in Brentwood, or in New York-or even in our hotel room down here. But maybe you won't feel so lucky if you remember that we were met at the airport here by the chief of police. I suppose you did see him, didn't you?"

"Of course we saw him!" Constanza snapped. Then he laughed, as if to make it clear that Ken's recital of their previous failures merely amused him. "And what does he matter? If he inquires for you at the Altamira, he will be told you have checked out. And that will be that."

"But didn't you wonder why he happened to meet us?" Ken asked. "Did you know it was because we have a friend in the Mexican federal police? And did you know that we wrote our friend yesterday, describing both you and your car-and telling him everything we knew about you? He will expect a phone call from us tomorrow morning-and if he doesn't get it, Captain Morro here in San Cristobal will be looking for us-and you." He made himself grin toward the blur that was Constanza's face behind his flashlight. "So you see we aren't quite as stupid as you thought-at least in the matter of protecting ourselves."

Adalco took a threatening step toward him. "You're lying!"

"No, Adalco," Constanza said slowly. "I don't think he is-not altogether. To be on the safe side, we will accept the whole story as true, and we will act accordingly. A few minor changes in our plan will be necessary-but now that we have been obligingly informed of the potential danger, we can easily meet it." He nudged Ken with his foot. "Get up! We can waste no more time."

Ken felt a sinking sensation in his stomach at Constanza's cool reaction. These men might be braggarts, but Constanza at least was no fool.

And then Adalco was jerking Ken roughly to his feet, and the others were also being prodded upright.

The climb up the hill to the ruins had never seemed so steep. And at the top they barely had time to catch their breath, under Constanza's sharp eye and ready gun, while Adalco made a hurried measurement with a compass and a surveyor's tape.

"All right," Adalco said then. "This is the spot."

The spot he indicated, inside what Ken realized had once been the patio of the Obregon house, was covered with several feet of what appeared to be a crumbled masonry wall. Removing it would be hard and heavy work.

"Get the tools," Constanza told Adalco, and continued to stand guard over the boys until the latter returned. "Now," Constanza went on, speaking to the boys, "we will free your hands so that you can dig. But do not make one more mistake and think you can attempt to run away. One of you might make it." He paused. "But two of you," he added quietly, "will not."

Adalco's knife cut quickly through the cords. Then he stepped back a few paces, took out his own gun again, and turned it and his flashlight on the boys. "We are waiting," he said. "Dig."

Constanza added, "Clear an area three meters- nine feet-square." As he spoke, he sat down where he could lean his back against a tree. Adalco joined him.

Sandy picked up the crowbar and drove its point under a compact mass of the rubble. Then he threw his weight on the end of the twenty-pound bar and lifted the mass of stone high enough for Ken and Ricardo to wedge their shovels under it. Then the three heaved together, and slowly, an inch at a time, they moved the massive lump off to one side.

Sandy chose another target. Once again he drove the crowbar beneath a heavy weight of stone, and again the others joined him to move it.

Adalco had laid his gun on the ground, beside the place where he was sitting. He had cut a thin tree branch, and was slashing off the leaves and twigs. Suddenly he flicked at the air with the flexible seven-foot switch he had contrived. "Maybe this will help to speed you along," he said, and flicked the switch again, this time at Sandy's legs.

The big redhead straightened. He looked full at his tormentor. "Do that again," he said, "and you'll dig your own hole."

The reaction was instantaneous. The switch lashed swiftly through the air, aimed at Sandy's cheek.

"Keep your mouth shut!” Adalco ordered, as the whip moved. "You-"

His words ended in a gasp. Sandy had caught the end of the switch and yanked it out of the man's hand with such force that Adalco was jerked forward on his knees.

"Get back!” Constanza was on his feet, his gun pointed at Sandy. And then the gun spit flame, and a puff of dust erupted at Sandy's feet.

CHAPTER XIV

DEAD END

"Sandy!" Ken grabbed the redhead's arm in a crushing grip. "Stop!"

"All right," Sandy said quietly. His voice told Ken that Sandy realized how ruthless Constanza could be.

Adalco had grabbed the stripped branch again and was lurching to his feet. "Now I'll show you what a whipping really is! Now-"

"That's enough, Adalco I" Constanza's words stopped the other man short. "Let them get on with it," he said. "Go on-clear that ground and start digging!" he ordered the boys.

It took an hour to remove the thick layer of rubble from an area roughly nine feet square. All three boys were aching with weariness by the time the debris was piled around them in a wall more than three feet high. Their clothes were soaked with perspiration that made them shiver in the cold night air.

When they cleared away the last shovelful of stones and adobe bricks, Adalco ordered them to start on the earth beneath. "There can't be much of it," he barked. "The stones of the old courtyard ought to be right under there. Hurry!" he added shrilly. "Get at it!"

Without looking at him, Sandy raised the crowbar and drove it into the loose earth. The steel point penetrated only a few inches of soil; then, with an unmistakable sound, struck heavily against stone.

"Did you hear that?" Adalco demanded triumphantly of his partner.

Ken and Ricardo attacked the soil with their shovels, and Sandy loosened more of it with the point of his crowbar.

Suddenly the beam of Adalco's downward-aimed flashlight illuminated an area of cleared flagstone. Five minutes later the boys had exposed two big flat stones, each about two feet square.

"Pry one of them up!" Adalco commanded.

"All right." Sandy barely choked out the words. "Grab it when I lift up with the bar," and he jammed the steel point under the stone and bore down on the handle of the heavy tool.

Ken and Ricardo clutched the raised edge of the flat stone with blistered hands, and heaved it upward until it stood on its rim.

Beneath it was a smooth expanse of solid earth. Sandy rammed the crowbar point into it, to prove to the men watching from above that the stone had lain on packed soil.

"Let that one go," Constanza commanded shortly. "Try the other one."

The process repeated itself. The other exposed stone also covered nothing but hard earth.

"All right," Constanza said. "Clear another stone."

The next one they uncovered was slightly larger than the first two. Sandy dropped the point of his crowbar on it-and it rang with a hollow sound.

Ken's heart jumped. His eyes met Sandy's and Ricardo's. For a moment they all forgot the grimness of their situation, as they realized that they must actually be standing above the entrance to the tunnel that they had been discussing since that night in New York, which now seemed so long ago.

"Did you hear that?" Adalco said excitedly. He was leaning so far forward toward Constanza, on the other side of the excavation, that it seemed he would lose his balance. He jabbed at Sandy's bent back with his flashlight. "Pick it up, fool! Pick it up! Lift-!"

His mouth was still open on the word when Sandy swung around with lightninglike speed, his outstretched arm striking Adalco's and knocking the flashlight to the exposed stones. It was rolling toward Ricardo's feet as Sandy's right arm came around like a flail to strike Adalco's abdomen.

The man jackknifed, gasping for air.

Constanza bent forward, as if to jump down onto the flagstones, lost his footing, and balanced precariously for a moment on his perch. Then he toppled backward. But he managed to land on his feet, outside the wall of debris. And even as he straightened, his gun arm moved back into position and the weapon pointed toward Sandy.

Ken's hand closed swiftly around a lump of packed earth. Like the stroke of a catapult, his arm moved back and then forward, and the missile flew toward its target. It struck Constanza on the chest, shattering in an explosion of grit and dust. The man's arm flew up instinctively toward his eyes. His gun cracked, stabbing a flame skyward into the night.

In the same instant Sandy, reversing his original spin, had let his fist connect with the point of Adalco's forward-thrust jaw. The man snapped upright under the staggering power of the blow. His back arched. His feet lifted. He crashed backward off the pile of debris, landing on his head. With his feet upturned, on the stones at the bottom of the pile, he lay still.

Ricardo snatched up the flashlight that had rolled close to his feet and turned it on Constanza, recovering now from the surprise of Ken's attack. The man's mouth twisted in an ugly snarl. He was bringing his gun into position again, aiming it at Sandy's towering head.

"Down!” Ken yelled in warning, and threw himself in a flying tackle that felled the redhead amid the spray of dirt thrown by the second bullet from Constanza's gun.

"I'll take care of you-all of you-right now!" Constanza's threatening words were spoken with deadly menace. Slowly he took one step and then another toward the wall of rubble that separated him from the boys. His flashlight was aimed at them from one hand, his gun from the other.

Ricardo crouched swiftly, grabbed a clod of earth, and hurled it with all his strength as he came erect again. Even before the missile struck the flashlight, and knocked it out of Constanza's grasp, Ricardo was feeling for another clod.

Sandy swung with lightninglike speed

"Throw something!” he begged Ken and Sandy in a choked voice.

Now the light in Ricardo's hand was the only one illuminating the dark night. He kept it pointed at Constanza as the man crouched, fumbling for the flash he had dropped.

In the shadow beneath the beam from Ricardo's light, Ken disentangled himself from Sandy and grabbed a stone as he came to his feet. He threw it so swiftly that he had no time to aim, but he saw it strike the man's shoulder before he dropped down again behind the protective wall of debris.

Constanza's gun went off in the same instant, but Ken's blow had jarred the man's arm. His third bullet smacked harmlessly into the piled rock.

Ricardo had turned off his flashlight, leaving them all in total darkness. As Ken felt for another weapon, Sandy whispered, "Light him up a second! Now!"

Ricardo's light flashed, found Constanza, and pinpointed him briefly. Sandy let fly a stone the size of his fist. The light went off.

Constanza howled in pain. But an instant later a beam of light angled over the boys' heads. He had recovered his flashlight.

"Adalco!” the man shouted. His light pointed downward, first on one side of him, then on the other, then flat across the wall of debris again.

Ken had temporarily forgotten the other man. Now he realized, with a sense of desperation, that if Adalco was conscious, and still had his gun, there was no longer the faintest hope that Sandy and Ricardo and himself would escape with their lives.

Constanza himself would never risk coming close enough to the wall to aim either his light or his gun down on the boys crouching below it. The boys could strike him down with hand-hurled weapons before he was in a position to fire. But with Adalco's help he would be able to accomplish what he couldn't do alone. No matter where the boys crouched, they would be a target for one of the two men stationed on opposite sides of the excavation.

"Adalco!" Constanza called again.

The movement of his light told the boys that he was beginning to edge slowly around the wall toward his confederate on the other side.

"Can we get Adalco in here-use him as a hostage?" Ken breathed.

"We can try."

Ken sensed Sandy, beside him, starting to crawl across the flagstones. Ken started to move after him.

Instantly Constanza's light flashed down from above into their traplike enclosure and illuminated Sandy's outstretched hand. Sandy drew it back as if he had been burned.

Constanza laughed. "You're finished now!" Then he said, "Adalco! in a tone of voice which told the boys that he had reached the other man. "Get up!” he urged. "Here, man-wake up!” The sound of a sharp slap told the boys that he was trying to stir Adalco back to consciousness. "That's it! Open your eyes!"

It was a matter of minutes now, Ken told himself. For a split second he remembered the excitement he had shared the night Sandy opened Ricardo's amulet, and first exposed the treasure map inside it. If they could have realized then-

Suddenly he grabbed Sandy's arm, close beside his. "KEX!" he breathed. "KEX!" And when Sandy didn't instantly respond, he whispered hurriedly, "That's the design of the tunnels! Don't you remember? The entrance must be right here-and there's an exit too!"

Ricardo had heard him. Now their three heads were close together.

"At the bottom of the vertical stroke of the K," Sandy said suddenly. "Sure! Let's get this stone up!"

"Get up, Adalco!" Constanza was urging insistently.

His words were followed by a confused mumble. Adalco was coming around.

Sandy had found the crowbar, slid it under the big flagstone, and was bearing down. Ken and Ricardo got their hands under the raised edge and heaved. Slowly the stone came upward, and a dank, musty odor rushed out of the emptiness beneath it.

"The light," Ken whispered, when the stone stood on its edge.

Ricardo shone his flashlight briefly, and then turned it off again. They had all seen the flight of perhaps half a dozen rough stone steps leading down to a stone floor.

"You first, Ricardo," Ken said.

Constanza's voice sounded over his. "On your feet, man!"

Ricardo didn't hesitate. Then, below the surface, and safe from detection from the far side of the wall, he turned on his flashlight.

Sandy gestured Ken to go next, and followed as soon as Ken had negotiated the first few steps. Ken felt the small thud when Sandy eased the big stone back into place above his head.

An instant later they were all three standing side by side at the foot of the stairs. The tunnel they were in was high enough so that even Sandy could stand erect, and wide enough for two to walk abreast in it. The walls were of well-fitted stones, and the stone slabs that formed the ceiling were long enough to reach from one wall to the other. The stone floor under their feet was covered with dust, but smooth and well laid.

"We're at the northeast corner of the tunnel." Ken took the photograph of the map out of his pocket and held it in the light. "We're at die top right point of the X. And the exit's at the southwest corner, at the foot of the K."

"Right," Sandy agreed. "So we should follow this tunnel straight ahead-crossing the other bar of the X-until we reach the lower-right corner. Then well be at the end of the bottom stroke of the E. Come on."

In the confines of the tunnel, Ricardo's light cast its beam far ahead. They could see the crossing of the X before they reached it. They paused at the intersection only long enough to shine the light down the crossing tunnel, which stretched into the darkness on each side of them. Then they hurried on.

"We figured that one leg of the X was about a hundred and twenty-five feet long," Sandy muttered. "Seems as if we've gone that far already. The air's none too good in here."

"There's enough oxygen in here to last us until we get out," Ken said.

Ricardo's light came up against a blank wall. They had reached the bottom of the X. But the tunnel turned to their right, and they followed it into what they thought of as the bottom stroke of the E.

Some fifty feet brought them to the end of that stroke, and a branching of the tunnel. One branch went sharply to their right, to form the upright of the E. The other veered toward the right at a oroad angle, forming the lower sloping line of the letter K.

"We take the angle," Sandy said. "And in about seventy-five feet we should come to a three-way branch-one for the upper slanting line of the K, one for the top half of its upright, with your plumed serpent at its end, one for the lower half. We turn left toward the bottom of the K."

They had been inside the tunnel for only a few minutes, but they knew their disappearance would have been noticed almost immediately. At any moment they expected to hear the sounds of pursuit.

They all caught their breath as they approached the last junction. Now, they should be within some fifty feet of the spot marked sdida peligrosar-dangerous exit.

"I don't care how peligrosa it is," Sandy breathed. "It can be strewn with broken glass-or open up into a nest of cobras. We're going to take it."

The tunnel widened out at the point where it branched. Ricardo turned his flash immediately into the branch that angled sharply left from where they stood, and the others were close behind him as he moved into it.

At the end of five steps he stopped dead. Ahead of them rose a jumbled mass of debris. Huge slabs of stone from the caved-in ceiling formed the bottom of the mass. Above it were tons of earth that had fallen when the ceiling gave way. Together they formed a barrier that completely blocked the passageway.

"Peligrosa isn't quite the word." Sandy's flat voice broke the stunned silence. "We're trapped-done for."

"Not yet!" Ken said suddenly, after another long moment of silence. "We've still got a chance! We can lose them in here-get around behind them and then go back out the way we came in!" He turned on his heel. "Come on! We'll get up into the upper part of the K or the E-" He didn't bother to finish. The others were close behind him by the time he reached the junction at the center of the K.

Ken stopped there, facing east, with one tunnel slanting off to his right and one to his left. They had come by the former.

"They'll probably come that way too," he told the others. "But we can wait here and make sure. We'll see their light even before they turn into that tunnel from the E, and that will give us time to take off in the other direction. Either way will take us back to the stairs. Turn our light off, Ricardo," he added. "We don't want them to see a glow up here at the same time we see theirs."

Slowly the seconds ticked away in the heavy darkness. Now the oppressiveness of the air was more apparent than ever. Ken found himself trying to take a deep breath, and failing.

They stood close together, in complete silence, ears straining for the first sound that would tell them that Constanza and Adalco were also inside the tunnel.

They all heard it-a faint distant voice that grew louder until the anger in it was plain to hear. Then a second voice sounded.

Ken covered his ears briefly, and then listened again. "It's confusing down here," he whispered. "You can't really tell which direction the voices are coming from. First it sounds like one side, then-" He broke off. They had all seen the glow of light that suddenly appeared in the distance toward their right-at the junction of the K and the E.

Ken spoke softly. "They're coming the way we came. So we'll-"

Even as he spoke they were all turning into the tunnel that angled off to their left, moving forward by feeling their way along the stone wall.

They had taken only half a dozen steps when they froze. Ahead of them, in the distance, was a second light.

Then they saw the flaring torch appear in plain view around the corner-a resinous pine limb burning with a smoky red flame, carried high by an advancing figure dimly lighted in its glow.

Sandy had been right after all. Constanza and Adalco had trapped them-were coming at them from two directions, to herd them into a dead end of the tunnel from which there was no escape.

CHAPTER XV

SEALED OFF

Without realizing it, the boys had backed away from the two approaching lights. Suddenly they found themselves against the wall. The two lights were still visible, moving toward them at an angle, one from the left, one from the right.

Straight toward their right the tunnel-the lower half of the upright of the K-was blocked by the fallen earth and stone. But straight toward their left it stretched away in darkness toward the top of the K, where the map had shown the tiny drawing of a plumed serpent in the last curved section of the passage.

Ken moved dry lips. "Maybe we can hold them off at that curve," he whispered, and thrust Sandy and Ricardo into the darkness of the tunnel to their left.

"You take this." Ricardo pushed the flashlight into Ken's hand.

Ken waited until they had moved several yards, feeling their way along the wall, before he flicked on the light. The sight it illuminated made them all gasp.

Just ahead of them was what appeared to be a rough, uneven platform. It had been formed by the collapse of several great ceiling stones, which now lay broken and overlapping each other on the tunnel floor. And beyond the platform was a fantastic jumble of stone-ceiling blocks which had become loosened, some on one side, some on the other, and fallen diagonally across the tunnel to form a crisscrossed barrier resembling a heap of giant jack-straws. The roof of the tunnel above the collapsed stones was raw earth, pockmarked with holes that showed the source of the clods and small rocks scattered over the larger stones.

At first glance it seemed to Ken that the tunnel ahead of them was as effectively blocked as the section which led to the exit marked on the map. Then he moved forward, exploring with his light, and saw that it would be possible to crawl among the collapsed stones to a section of clear tunnel beyond them.

"Let's go," he whispered. "But be careful."

At last he was on the far side of the barrier, holding his breath until Sandy and Ricardo joined him there. Sandy, the last one through, was just coming erect from a crawling position when the beam of Constanza's light struck through the angled openings among the upper portions of stone in bunding points of light.

"Down!" Ken breathed, flicking off his own flash as they all dropped to their knees.

At that level they could see nothing. To a height of some three feet from the tunnel floor the big stone slabs, and the debris fallen among them, formed an impenetrable obstacle to the rays of Constanza's light. Therefore, Ken realized, so long as they were on their knees, that same obstacle would protect them. But if they stood erect again they would be exposed to bullets that might be aimed straight through the one unblocked section of the tunnel, near the roof. Only there did the position of the fallen stones leave a sizable, clear channel through the barrier.

Sandy found Ken's hand, closed it over a stone, and whispered, "Collect more of these."

Adalco's voice, sounding terrifyingly close, shouted suddenly from the other side of the barrier. "Come back out of there 1 It doesn't go anywhere, you crazy fools! Don't you know you're trapped?"

Sandy sprang upright, his head and shoulders outlined for a brief instant in the light pouring through the open channel at the top of the barrier. There was a stone in his hand, and his arm was flung back. Then the arm shot forward and the stone skimmed through the tubelike passageway as a bullet moves through a rifle barrel.

Sandy was flat on the ground again before Adalco's shrill cry of pain and rage sounded, followed by the reverberating roar of a gun.

Three shots in quick succession echoed and reechoed in the close confines of the tunnel.

Over the noise of the firing, Constanza spoke sharp, rapid Spanish.

"He's saying," Ricardo whispered, "that they should get back out of range."

"Let's encourage them," Sandy said. While the third shot was still ringing in their ears, Sandy rose and hurled another stone through to the far side of the barrier.

Once again there were three shots, more violent Spanish from Constanza, and then the sound of footsteps thudding on gritty stone. The glow filtering through the barrier became fainter.

Sandy risked a quick look. "They've backed away -down almost as far as the junction," he reported when he crouched down again.

"But we can't get out of here as long as-" Ken stopped. "Listen!" he whispered. Then he directed Sandy's attention upward.

From the earth ceiling of the tunnel, above the collapsed stone slabs, tiny pebbles and bits of earth were falling. In the dim light they looked like rain and hail-first a spatter from one side of the ceiling, then a heavier downpour from the other, then several spatters here and there.

"Loosened by the concussion of the shots," Sandy whispered grimly.

"And any more shots-" Ken didn't bother to complete the sentence. If tons of earth fell from the ceiling, they would be sealed up behind a barrier more impenetrable than a wall.

Staccato Spanish sounded from down the tunnel. Ricardo caught his breath, listening, and then translated in a thin whisper: "They have heard the falling earth and stones too. They say-Constanza says- that it is very convenient, that everything happens for the best. He says-"

A shot drowned out Ricardo's voice. A second and a third followed it. The roar was so loud that Ken's hands went instinctively to his ears. But he couldn't shut out the sight of a sudden, dark cascade from the ceiling upon the collapsed slabs beneath.

Dust filled the air in a choking cloud that hid the avalanching earth and stone. But its ominous rumble sounded steadily louder and louder.

Then the rumble was punctuated by a jarring crashing thud of a heavy ceiling slab.

While the loose earth and pebbles continued to fall with a noise greater than a tropical downpour on a tin roof, the heavy slabs of stone crashed from their age-old positions one after the other with ponderous slowness-each one, as it fell, supplying the thud that jarred the next one loose.

Trembling, choking with dust, the boys moved backward away from the thundering wave of destruction.

When Ken recovered enough to turn on the flashlight, and swing around to guide their steps with its light, he found the tunnel curving to the left just ahead of them. "It'll be better up there," he gasped, urging the others on around the bend.

They were sucking in their first breath of clearer air when they realized that the flashlight beam's end was striking the stone wall that marked the end of the tunnel, several yards beyond the curve. It seemed to be a single huge slab of stone, and on it was carved a grotesque shape that appeared to move as the flashlight shook in Ken's hand-a seated human figure with a towering headdress and a face that looked like the head of a serpent.

Ricardo was the only one of them who continued to move forward. He walked slowly, a look of wondering amazement on his face.

"The plumed serpent!" Ricardo said softly.

Suddenly Sandy said, "Listen! There's no noise any more! The ceiling has stopped falling! Let's go take a look!" He grabbed the flashlight from Ken's hand, turned back, and disappeared around the curve again. An instant later he was saying, "Come here! Quick!" And he flashed the beam back to light their way.

Ken caught the arm of a dazed Ricardo and pulled him along. And then they were both looking up at the spot toward which Sandy was aiming the flashlight.

In the wall of the tunnel, beginning on a level with Sandy's shoulder and reaching to the ceiling, was a gaping hole perhaps four feet square. The two slabs of stone that had once filled it now lay on the floor at Sandy's feet, above one of the big ceiling slabs that had also fallen at that point. Ken didn't remember stumbling over them when he passed the spot earlier. He realized they must have come down in the past few minutes.

"Is it a way out?" he asked.

Sandy was shaking his head oddly. "I don't know. But look!" Now he pointed the flashlight directly into the hole, and Ken and Ricardo both stood on tiptoe to see into the dark cavernlike opening.

"Skeletons!" Ken breathed. "This must be an Indian tomb! Look-they've got beads around their necks! And bracelets!"

"O.K.," Sandy said grimly. "That's what I thought they were too. But I figured maybe I was seeing things. Now I’ll crawl up there and see if there's any way out through-"

"But you might disturb the tomb!" Ricardo broke in. "And the archaeologists must see it just as it is. Perhaps it is a most important find!"

"Archaeologists may be finding our skeletons someday if we don't get out of here," Sandy told him. "And our only exit may be through here."

"You don't need to crawl in," Ken said. "Move the flashlight around. You can explore with that. See- the wall to the right is just earth and pebbles-there couldn't be any exit there. If the others are the same-"

"Guess you're right." Carefully Sandy moved the beam around the two-foot-high enclosure. It was barely six feet square. Its three remaining walls were earth. Its ceiling was formed of three long slabs of stone.

"You're right," Sandy said finally. "There's no use wasting time in there. And if we're totally closed off in that direction-" He turned the flash down the tunnel, toward the barricade of stone slabs on which so many more stones had fallen since the boys made their way through it.

The dust was settling now. The flashlight showed a sloping wall of earth and stone, beginning not more than a dozen feet from where the boys stood, and angling up toward the ceiling.

Sandy ran the light over it slowly, as if to postpone the moment of discovering that it formed a totally impassable barrier. Suddenly the light paused and steadied. It was pointing at a gap scarcely larger than a man's hand, just beneath the ceiling near the center of the barricade.

Ken's mind began to race. He was sure Constanza and Adalco believed they had locked the boys inside the tunnel. Presumably the men had then hastened to find and carry away the treasure. They might already be outside the tunnel, and on their way to some unknown destination. And in that case it would be safe to climb carefully up to that small gap, and to enlarge it inch by inch until-

A voice, sounding far away and speaking Spanish, intruded on Ken's thoughts.

"Did you hear that?" Sandy whispered. "They're still there! Listen!"

Ricardo moved silently forward. And then he turned around and came back. He waited until he was close to Ken and Sandy, and then he said softly, "I don't understand! Constanza and Adalco-they are both there-just on the other side!" He gestured back over his shoulder toward the barricade. "And they are digging the stones away! They are very angry. They are saying they should never have started the cave-in until they made sure we didn't have the treasure!"

"We?" Sandy echoed blankly.

"That's what they said. They think we have it with us-in here."

"I suppose that means the treasure is missing," Ken said slowly. "But if they're going to break a way through that barricade because they think it's in here, they'll at least give us a way out."

"But will they let us use it?" Sandy asked grimly, and answered his own question. "You know they won't. They'll open fire the minute they can get a sight on us."

"You're probably right," Ken said. "Our only chance is to be on the other side of that curve when they break through. Then, if we keep a barrage of stones going-"

As he spoke the last words they heard a strangled shout of terror, and the thud of a huge slab of stone falling on stone. At the same time, earth and pebbles rained down on their heads, and choking dust once more filled the tunnel.

Sandy aimed the flash at the top of the barricade, toward the opening through which Ricardo had heard the voices speaking on the other side. Even through the millions of particles of dust in the air, it was possible to see that the opening was gone now.

"Their digging-it's started the stuff falling again!" Sandy gasped out the words. "They won't ever get through that barricade now. Nobody will!"

CHAPTER XVI

THE PLUMED SERPENT

Half a minute later, coughing and stumbling, they had made their way back to the end of the cul-de-sac, to huddle against the stone carving that Ricardo had called the plumed serpent. Even there the dust followed them, and they found it difficult to breathe.

"The dust-will-settle in a minute," Ken managed, hoping he was speaking the truth. But he knew as he said the words that even if they were true the situation was still hopeless.

For a moment none of them spoke. Then Ricardo said, "I do not know-how to say this. But I would want you to know that I am sorry I ever wrote to you-or came to see you. I think we will never get out of here-and-"

"Stop that!" Sandy broke in. "It's no more your fault than ours that-" He began to cough again and couldn't finish.

"Of course it isn't your fault, Ricardo," Ken said. "You didn't drag us into this-we dragged you." He was thinking again of the night when they had first seen the map, and how they had pored over it breathlessly while Ricardo translated the words written in tiny black letters on the thin paper-entrada, tesoro . . .

On a sudden impulse Ken pulled the map photograph out of his pocket and spread it in the light of the flash that he took from Sandy. He told himself it was futile. But the wild hope flamed in his mind that somehow it would have a new message for them, now, that would show them a way out of the living tomb in which they were trapped.

Sandy sensed what Ken was thinking. "It's no use," he said. "I remember the whole thing, and-"

"We didn't remember that the words techo bajo- low roof-are written in right at the place where the barricade is now," Ken said. "That must mean that those ceiling stones had begun to sag when the map was made.' He moved the map so that Sandy and Ricardo could see it too.

"I don't know what good it did them to write the words in, come to think of it," Ken went on. "And what's the point of some of the other words? Up here at the top of the K, where it says manatid. That means a spring, doesn't it?"

"Yes," Ricardo replied.

"But why should anyone want to know about that spring?" Ken continued. "If you came in the way we did, you could get to the treasure without passing the spring or the low-roofed part. And if you went out the same way, you wouldn't have to pass the spring or the low roof, either. So why write the words-?"

"Who knows?" There was an edge of panic in Sandy's voice. "We're looking for a way out of here, not an answer to a riddle."

"This is going to sound crazy, but listen," Ken went on, as if he hadn't even heard Sandy's outburst. "Suppose there is a reason for writing those words on the map. Suppose this letter S beside the little drawing of the plumed serpent doesn't stand for serpiente, as we thought. Suppose it stands for salida instead- exit. Suppose there is a way out here." He looked up at Sandy and Ricardo. "Then there'd be a reason for writing those words on the map."

Sandy already had his knife out of his pocket, and was tugging at the blade. "Ken," he said hoarsely, "if you've- Let me have the flashlight over here. Quick!”

Ken turned the glow on the carved stone. The light flickered, steadied, and then flickered again. "This is not going to last much longer," he murmured.

Sandy sent him a look of grim determination. "We may not need much light," he said. "If that S stands for salida, and there's an exit here somewhere- Don't worry. We'll find it in the dark, if we have to."

"Ken! Sandy!" Ricardo was close beside them. "I understand what you think. But the carving is all on one stone. You can see that. It is not several stones put together, or-"

"And who says this whole big stone isn't a door?" Sandy demanded. He had taken the flashlight in his own hand, and was standing on tiptoe to look at the crack between the top of the carved stone and the row of other smaller stones that framed it. Then he slid his blade into the crack carefully. "It goes in the whole way!" he announced, showing them that only the handle of the knife now protruded.

Slowly he drew the knife along the crack. It moved without stopping, from one side of the stone to the other.

Then Sandy withdrew the knife, and inserted it again at a right angle, in the crack between the left side of the carved stones and the bordering frame. Once more the blade slid out of sight. Once more Sandy drew the blade the full length of that side of the big stone.

"Now the bottom!" Ken barely breathed the words.

As the blade traveled laterally again Sandy had to stop and withdraw it twice. Obstructions had prevented it from moving straight from one side to the other. But for most of the distance there seemed to be a clear space between the big stone and the slabs that formed the tunnel floor.

Thirty seconds later Sandy had slid the blade of his knife down the remaining side. "Clear all around!" he said. "Or clear enough. Now all we have to do is get it open!" For a moment he studied the carving carefully. "There doesn't seem to be any protrusion big enough to be used as a handle," he said. "That must mean it opens outward-away from us." He took a deep breath, put his powerful shoulder against the carving, and pushed.

The stone didn't budge.

"Come on!" Sandy said. "All of us together!"

But the weight of the two additional figures made no difference. Three times they drove their shoulders against the carved surface, at Sandy's signal. The stone did not move.

"It's no use," Sandy said flatly. "Either it's not a door after all, or it was a door once and doesn't open any more. Or-" He snatched up the light from the floor where Ken had put it and moved it slowly back and forth over every inch of the upper half of the stone. He had reached as far as the figure's arm when he suddenly stopped, grabbed his knife out of his pocket again, and prodded at the carving at that point.

Dust scattered on the stone floor at his feet.

"Look!" Sandy said. "This part of the arm stands free of the rest of the stone. The opening was filled with dirt-but you can see it now. It makes this part of the arm a sort of handle. Here!" He thrust the light and the knife at Ken, clamped his two powerful hands around the carved arm, and pulled.

The stone still refused to move.

"This has got to be a handle!" Sandy said through clenched teeth. Once more he tugged on the stone arm. Once more it failed to budge from its position.

"Let us help," Ken urged.

"You can't," Sandy told him shortly. "There's only room for one pair of hands here."

"But there is room for this-no?" Ricardo had thrust forward the heavy leather belt he had unhooked from around his waist. "We can put the belt through the opening-and then we can all pull on the belt."

"Sure!" Sandy said quickly. "In fact we can use all three of our belts, to be on the safe side. Hurry up!"

Seconds later, three belts were looped around the stone arm and buckled.

"Ready?" Sandy looked at Ken and Ricardo.

Ken had his hands around his own belt. "Ready."

"Ready," Ricardo said, holding his Chamula Indian belt.

Sandy took hold too. "One-two-three-go!"

Three strips of leather snapped taut under the strain. Heels braced, three bodies leaned backward, each putting its full weight into the pull.

"Don't let go! Keep pulling!" Sandy gasped.

From the right-hand side of the stone came a faint grating sound, the scrape of stone on stone.

"It's moving!" Ken cried.

"Keep pulling!" Sandy shouted the words. "Keep pulling!"

Ken was closest to the right-hand side of the big stone. He saw it slide toward him, very slightly. The big stone was beginning to pivot on its left edge.

"More! More!" he begged. His own arms felt as if they were being pulled out of their sockets.

And then the stone was completely free of its frame on the right side. It moved with infinite slowness, a hairsbreadth at a time. It came away from its frame one full inch-two full niches.

Suddenly all three boys staggered backward, then-belts limp in then: hands. The door had suddenly begun to move easily.

Ken dropped his belt, clamped his hands around the edge of the stone, and moved backward with it. It swung on the big stone pivots that protruded from its top and bottom on the left side-pivots that moved in holes cut into one of the ceiling slabs and one of the paving stones of the floor.

Sandy and Ricardo were close. All three of them were peering into the utter blackness beyond the opening door.

"It's all right," Sandy said, his voice faint with relief. "I still can't see anything-but I can smell fresh air."

"Come on," Ken said, the moment the door opening was wide enough for them to squeeze past. He stepped through, the others at his heels.

The feeble flash still gave enough light to show that they were in another tunnel, apparently identical to the one they had left behind. At the end of fifteen feet it seemed to stop at the dead end of a stone wall. But Ken felt air move past his cheek, and he turned the light upward. The pale beam illuminated only the first few feet of a stone-lined shaft that went on up into darkness.

"This is where the air is coming from," he told the others.

"And look-there's a foothold!" Sandy explored with his hands. "And here's another." He stepped quickly up onto the first small outcropping, and then to the next. A moment later only his feet were visible. Then they, too, disappeared.

Ken and Ricardo could follow his progress by the sounds of his shoes and clothing brushing against stone-sounds that were amplified in the narrow shaft. The sounds halted abruptly. Then Sandy's exultant voice came down to them.

"I'm out! And it's dawn up here! And there's all the air in the world! Come on up!"

Ken sent Ricardo ahead. He followed immediately. It was a short climb, not more than twice his own height. Sandy was holding a bush aside. Ken stepped out into the open air. Sandy let the bush spring back into place. The opening through which Ken had emerged had all but disappeared-now it looked like nothing more than a shadow at the foot of a big boulder under leafy trees. Birds were chirping cheerfully and busily overhead. There was a pale sky beyond the branches.

Ken gulped in fresh air. The others were grinning at him. He grinned back.

"Where do you suppose we are?" he asked finally.

"Look!" Sandy turned him around and pointed. They were on the hill, less than a hundred feet below and to one side of the gateway through which they had stumbled some hours before, their hands bound, armed captors at their backs.

"Do you suppose they're still down in there-in the tunnel," Sandy said after a moment.

"For the answer to that question," Ken said firmly, "I am willing to wait until we're with Captain Morro and a couple of his men. Right now, I suggest we head for our car and then for San Cristobal."

"I think this is the wise thing to do," Ricardo said earnestly. His face was still pale and taut from the ordeal of the long night.

"Oh, I do too," Sandy agreed. "Who can tell? We might even find somebody willing to share their rice and sausage with three hungry strangers-three strangers who spent a hard night digging."

Eight hours later Ken looked up from his typewriter, stretched wearily, glanced at his wrist watch, and then grinned. "The next time I hear anyone say Mexicans are slow-moving, they'll get an argument from me," he said. "Do you realize it's just past two o'clock-that it was only about eight hours ago we crawled out of that tunnel?"

"That's impossible," Sandy said. Then he looked at his own watch and shook his head. "No, it isn't. You're right. But I never saw so much get done in any other eight hours in my life."

Before the first of those hours had passed, Captain Morro and several of his men had driven back with them to the hacienda, where they found Constanza and Adalco trapped beneath a heavy ceiling stone that had fallen across their legs.

Adalco had a broken foot. Constanza's right leg was fractured. Both were bruised and lacerated. Each man was also violently bitter against the other, for the failure of their plans, and in their angry bitterness they both talked at length.

Much of what they said, Ken had guessed at earlier. It was true that the Obregons had buried the bulk of their wealth in the tunnel, and described its location in two maps, neither of which could be used without the other. It was also true that Ricardo's grandfather, following the instructions of his employer, had sent one of those maps and a letter to the only surviving member of the Obregon family -a man then living in Spain. But that man had died soon afterward. All his papers, including the letter and the map, had lain for years in a chest, while his house remained closed and unoccupied during interminable legal squabbles that prevented its sale. It had finally gone on the market only two years earlier and Constanza had bought it. He had opened the chest, to find part of its contents-including a page of the letter Ricardo's grandfather had written- destroyed by age and dampness. But the map itself, and the remnants of the letter, had been enough to send Constanza and Adalco, his partner in various dubious real-estate transactions, across the Atlantic to search for treasure.

Ken read over the last few sentences of the story he had been typing for Global News. "It must have cost them a pretty penny," he said, "to track down Ricardo, chase him all over North America, finally get the map away from him-and then find out the treasure was gone after all. Morro thinks it probably was stolen almost immediately, while the hacienda was being looted during the revolution."

"You feeling sorry for those two hoodlums now?" Sandy, finishing the address on a package of exposed film, cocked an eyebrow at Ken. "We're the ones you ought to worry about-you and Ricardo and me risking our necks on a treasure hunt that was a total flop."

"Hardly that, gentlemen."

Ken and Sandy looked up. Ricardo and two men in earth-stained clothes had just joined them in the small police-headquarters room that Morro had put at their disposal. Ricardo's eyes were shining. The two men looked almost as excited as he did. It was one of them who had spoken. Both were archaeologists who had arrived two hours earlier, having flown down from Mexico City.

The one who had spoken repeated his words. "Hardly that, gentlemen," he said. "No boxes of family silver, or chests of ill-gotten Obregon gold could be as important as what we've just seen." He shook his head in wonder. "You know," he went on, "when Gonzalez phoned us from Merida this morning- right after you had called him-and told us we should get down here immediately, it was hard to take him seriously. After all, Gonzalez is a policeman -not an archaeologist. But he is a good friend, and so we came. Thank heaven we did! To think someone else might have seen that crypt first!"

"Someone else did, of course." The second archaeologist grinned at Ken and Sandy, and clapped Ricardo on the shoulder.

"They think the tomb is very important," Ricardo spoke up eagerly. "Those beads and necklaces are jade! And they think there may be more tombs- that perhaps the whole tunnel was built centuries ago by the Indians, and the Obregons only found it and made use of it. Of course, it will be necessary to do much work in order to learn how old the tomb is-how long ago those skeletons were buried. But Senor Fernando says," he added, glancing shyly at the archaeologist who had spoken first, "that the plumed serpent is one of the finest he has ever seen- truly a great discovery!"

Ken grinned at him affectionately. "That's wonderful! And in the Global News story, at least, the discoverer of the important new plumed serpent will be Ricardo Montez."

"Oh, no!" Ricardo sounded shocked. "Please, Ken, you should not-"

Fernando stopped him with a laugh. "Don't worry, Ricardo. That's just what the story should say. We certainly won't contradict it. You three have already given us the most remarkable day of our lives. And if there is ever anything we can do for any of you, just let us know."

"There is, I think," Ken said. He looked at Ricardo and then hastily away again. "Ricardo here," he hurried on, "has been studying agriculture, as I guess he told you. But more than anything in the world he wants to be an archaeologist. You could help him- couldn't you?"

"Ken!" Ricardo almost shouted the word. His face was scarlet.

Fernando and his fellow scientist were eying him skeptically. "Does he know it means a great many years of study-and much hard work?"

"I think he knows that," Ken said firmly. "Of course he has no money to pay for years at a university-"

"That is not important." Fernando waved an impatient hand. "There are government scholarships for deserving cases. But the hard work-many grow tired of that." Suddenly he swung the full gaze of his penetrating eyes on the Mexican boy. "Tell me, Ricardo, would you like to work with us this summer? We'd soon find out if you've got the patience, the perseverance, and the feel for our work."

Ricardo didn't have to put his reply into words. The blaze of excitement on his face was enough.

Sandy smiled. "I'm glad I got a picture of Ricardo standing next to his plumed serpent," he added. "If you've got the right lead on your story, Granger ought to use it for the center spot on what is going to be one of my best picture spreads."

Ken was putting a new sheet of paper in the typewriter. "I'll have the right lead, all right."

Captain Morro, his uniform as rumpled as it was on the day they first saw him, appeared in the doorway. "Captain Gonzalez has just telephone from M6rida," he said, beaming. Then he completed his speech in Spanish, and gestured to Ricardo to translate for Ken and Sandy.

Ricardo was still having trouble finding his voice. "Your friend the captain is coming here tonight," he managed. "He says he wishes to apologize to you- for asking you to dig in his garden, he said-by buying you the best dinner in San Cristobal de las Casas."

"Now there's a man who knows how to make a truly handsome apology," Sandy said. "It's a skill I suppose I ought to pick up one of these days," he added quietly to Ken, as one of the archaeologists began talking earnestly to Ricardo. "I seem to recall making a good many rude remarks to you about a certain hunch you had some days ago."

"Think nothing of it." Ken glanced at Ricardo's happy face. "This particular hunch turned out pretty well," he admitted. "But I've had a few that didn't- and I'm likely to have some more."

"What! A mastermind like you?" Sandy asked mockingly. "You mean there might come a day when you'll wish you had a nice sealed-up tunnel to crawl into?"

"I just said it was likely. I won't promise anything," Ken told him, grinning.

Neither of them could know right then, at a moment when all seemed well with the world, how close Sandy had come to foretelling what would happen in the adventure that came to be called The Mystery of the Sultan's Scimitar.

THE END

THE MYSTERY OF THE PLUMED SERPENT

A KEN HOLT Mystery, No. 17

By Bruce Campbell