AT once Bob and Joe were breathless with interest. They had often heard of Inca secrets but had thought them nothing more than myths. Now, as this strange old man stood before them, the youths wondered if there might have been some truth in the fantastic tales told of Inca mysteries.

The old man hesitated for several minutes, staring off into space. Then, when the youths were becoming impatient with the long silence, he continued, speaking in a low voice.

“Far, far away, in the heart of a huge mountain, is a narrow tunnel that leads to a large cavern of Inca secrets.” Again the stranger hesitated, looking below at Cuzco.

“Why doesn’t he hurry?” thought Joe, almost saying the words aloud.

Finally the old man continued.

“This cave is so large that it occupies the entire mountain,” he went on. “It is lighted with a strange brilliance, that comes mysteriously from the outside. But ah! The Incas were marvelous inventors. They could do many things that we Americans cannot do.”

“Then you are an American?” inquired Bob quickly.

The old man nodded.

“I spent my early years in the United States,” he explained. “Graduated from college and set out to be a scientist. Then I became interested in Inca ruins and came here to look for them. My entire lifetime I have spent in these mountains, looking for ruins and treasure.”

“Treasure?” cried Joe. “Is there treasure here?”

“Undoubtedly there is,” was the answer. “In fact I believe I have found some.”

The young men were all excitement.

“Tell us about it!” begged Joe.

“I am not certain that I have found any,” the stranger said. “But I came across a sort of bin that is covered with a heavy stone block. Alone I am not able to lift it off. I firmly believe that in the bin is something valuable. This is in that cave I told you about.” He stopped and glanced about; then, satisfied that no one else was near, he continued: “It is a long, hard journey to this wonderful place. There is a secret trail, that is known only to myself. And to add to that, there is a single entrance to the cave. It cannot be opened until you press a hidden button.”

He stopped a moment and gazed thoughtfully at the young men.

“You saved my life,” he went on, looking at Bob gratefully. “For this I will gladly give you half of any treasure in the bin, if we can find any. Will you make the trip with me?”

For a few moments the youths said nothing. They wondered if there was really any treasure in the bin. And they wondered, too, if it might be possible to locate still more in the near-by mountains.

“I am willing to go,” said Bob at last. “It won’t put us out any, I’m sure. I think we can arrange it some way. Maybe Dad——”

He got no further, for at that moment the old man raised a hand for silence.

“Of course your dad is all right,” he said conclusively. “But I do not wish to take anyone but you and your friend here with me. Even your father might without thinking tell someone about this secret, and then we would lose everything. And I want no one else to know.”

“Then,” began Bob, “you want only Joe Lewis here and myself—my name is Bob Holton—to go with you?”

“You are right,” came the reply. “And my name is Rander—Doctor Rander. I would be much better satisfied if only we three went.”

“I think it can be arranged,” Bob told him. “What direction do we have to go?”

“East. Almost straight east from Cuzco. But of course there are many roundabout paths that we must follow, and much of the way is over no trail at all.”

“We’ll let you know a little later, if that is all right,” said Bob. “Where can we get in touch with you?”

Dr. Rander explained that he was staying in a little adobe hut at the other edge of Cuzco and that he had a sufficient number of mules to carry the provisions needed.

“How soon do you want to start?” inquired Joe, who was anxious to make the trip.

“I am ready any time,” the old man said. “If you wish, we will start tomorrow.”

Bob explained that they would talk it over with their fathers and call on their friends that night. With this, the youths headed back to camp, not desiring to lose more time even in seeing the ruins at the top of the hill.

“What do you think of it?” asked Bob a little later, as he and his friend came in sight of the monoplane.

“I think a lot of it,” Joe answered. “Why, it will be wonderful!”

“Don’t be too sure that we can go,” Bob reminded him. “It all depends on what our dads think. If they’re afraid to let us leave the expedition and start out with this Dr. Rander, why, I suppose that will end it all. And the old man won’t let anyone else go with us.”

“Funny he’d tell us about that secret, isn’t it? If he had kept still, he’d have had all the treasure for himself. But then, I suppose he was so glad you saved his life that he was more than willing to let you in on it. Then, too, he’s not sure of finding it.”

At the camp, the boys found their fathers and others awaiting them.

“What do you think of the ruins?” asked Mr. Holton, as the chums came up.

“We don’t know much about them,” returned Joe. “But there’s something else we want to tell you.”

While the men listened, Joe told of seeing the old man climbing up the steep hill and of Bob’s saving his life when he fell. He told of the secret treasure that the stranger said was in the Andes, and of the old man’s desire for the two youths to accompany him in the mountains. He finished by saying that he believed it might be worth while to go.

“Perhaps you’re right,” came from Mr. Holton. “It might pay you to go with him. Do you think he can be trusted?” Mr. Holton had great faith in the judgment of his son and Joe.

“Don’t know why not,” said Bob. “He seemed so glad that he had not fallen down the cliff that he was happy to tell us about the treasure.”

“There isn’t a chance of his being crazy, is there?” asked Karl Sutman, who was also listening to the conversation.

“Oh, of course there’s a chance,” replied Bob, “but I’d be willing to bet anything that he isn’t.”

“We can go with him, can’t we?” queried Joe, glancing especially at his father. “We may find treasure, after all.”

“I see no reason why you shouldn’t,” came from Mr. Lewis. “Of course you’ll be careful. And there’s very little danger of getting lost, with all the native huts scattered about. What do you think, Howard?”

“Like you,” Mr. Holton replied. “After all, Bob and Joe are able to take care of themselves. If Karl will stay in the vicinity of Cuzco until they get back, it will ease matters some. Or, if the boys will be gone too long, Karl can come on with the rest of the expedition to the valley of the Comberciato, and then return later to pick up Bob and Joe in Cuzco.”

“I’ll be glad to do it,” Karl Sutman said, and so the matter remained settled.

That evening Bob and Joe went to Dr. Rander’s hut at the edge of Cuzco. The old man seemed glad to see them, offering them the best chairs he had.

“Now about the secrets,” he began, after he had closed the door and made sure that no one was near. “First of all, we must keep it strictly to ourselves. If, while on our way, anyone should ask why we are going into the mountains, we must not tell them.”

“For one thing, we’re going to take movies of the country,” said Joe, and then explained this in full to the old man.

The youths spent all evening at the old man’s hut. When at last they were ready to leave, they had agreed on one thing: They were to start early the next morning.

As they walked silently back to the camp, gazing up at the starlit sky, Bob and Joe wondered what would be their adventures for the next few weeks. Would they actually come into possession of valuable treasure?