RATHER nervously Joe unfolded the paper, hastily read it, and then gave a sigh of relief.

“Nothing wrong,” he told his friends. “Take a look.”

“H’m,” observed Bob. “He only says he’s going to land in a level field about a mile from here, and that he’d better take us up with him from there, instead of waiting till we get to Pasaje. No other place near to land on. Closes by saying everything is all right.”

“So he wants us to go up with him now,” mused Joe. “Doesn’t want to wait till we get to Pasaje. I hate to do that. I don’t like to leave Dr. Rander till we get to the town. It doesn’t seem right to come with him all this distance and then go off and leave him here in the mountains.”

“Don’t worry about me,” said the old explorer quickly. “I have been through these mountains alone many times. I can manage the mules all right. And the town can’t be far away.”

“We’d go with you anyway,” Bob told him, “only Karl says there isn’t another landing place near.”

Without loss of time the three continued toward the level spot on which the aviator had landed, at length coming in sight of the monoplane.

Karl rushed out to meet them, his face bright at finding that all were alive and well.

“You old rascal!” cried Joe, shaking the young man’s hand warmly.

“How’d you know we were here?” asked Bob, who was also very glad to see the aviator.

“I saw you,” Karl Sutman explained. “I thought I’d take a short flight over this section to see if I could locate you.”

“You did, all right.” Joe was delighted. “Found us away out here in the wilds.” He hesitated a moment and glanced at Dr. Rander. But the latter had already been introduced to Karl Sutman, and needed no introduction by the youths.

There was one question in the aviator’s mind that he could wait no longer to ask.

“The treasure you were searching for—did you find any?” he inquired. “And the Inca secrets, too. How about them?”

Bob smiled happily.

“We did,” he answered. “Found both the treasure and the secrets.”

When shown the little box of gold trinkets, Karl gasped in astonishment.

“Is that all you found?” he demanded. “I thought there might have been some gold statues, or the like.”

“If there were we couldn’t locate them,” Joe said. “We considered ourselves lucky in finding what we did. They are worth many hundreds of dollars, maybe thousands.”

“Dad and Mr. Lewis and the others—are they all right?” Bob was anxious to learn if any misfortune had befallen his father and friends.

“They’re still hunting for specimens,” returned the aviator. “Mr. Wallace fell down a mountain and hurt himself slightly, but he’s about all right now. And you should see the large collection of birds and animals they have.”

“We have something that may interest them,” declared Joe, and showed Karl the huge condor, at the same time telling about his narrow escape from death.

“Wow!” Karl exclaimed when the youth had finished. “And Bob and Doc Rander came to your rescue, did they? Good for them.”

It was later decided that Bob and Joe accompany Karl at once in the monoplane to the Comberciato River, where the chums’ fathers were collecting specimens. The old man explained that he did not mind going on alone to Pasaje, where he had business.

“But before you leave,” Dr. Rander began, “I want to divide the treasure with you fellows,” addressing Bob and Joe.

“Don’t give us half,” Joe said pleadingly. “After all, it was your efforts that located the secret mountain cavern.”

The old man held up a hand for silence.

“You forget that I owe my life to you,” he reminded them. “If it had not been for your coming to my rescue, I would not be here to enjoy the treasure.”

“But——” began Joe.

“Say no more,” Dr. Rander silenced him. “Half of the gold is yours.”

He spent the next half-hour in dividing the treasure, giving the boys a good share. They thanked him warmly, then turned to Karl Sutman.

“Can we get started before long?” asked Joe. “I’m anxious to see everybody.”

“Sure.” The aviator was willing. “Let’s get your stuff loaded in the ’plane.”

They worked steadily until noon, at which time everything that belonged to the youths was packed in the supply compartment of the monoplane.

After the meal they bade Dr. Rander an affectionate farewell and stepped into the cabin. Karl started the engine, and then, with a roar and a rush, they started rolling over the field.

The old man waved as they left the ground and headed toward the north. The last the air travelers saw of him he was getting the pack animals ready to finish the journey to Pasaje.

“I suppose we’ve seen the last of him,” remarked Bob, as they left the ground. “We may hear from him later, though. He has our addresses.”

“Rather an odd character, isn’t he?” said Joe. “Seems strange that he’d want to remain in these mountains all his life.”

During the next few hours Karl sent the airplane ahead over mountains that were more rugged than any the youths had ever seen before. He was steering the machine near Mount Panta and the locality in which were Dr. Rust and the other archÆologists when suddenly he found himself almost unconsciously entering a heavy cloud.

A second later, when he realized what he had done, the aviator saw that it was too late. Already the ’plane was in the midst of a heavy opaque atmosphere of white.

“I was a nut for getting in a place like this,” Karl said through the telephone. “And there’s no way of getting out now only to go on through it.”

Karl well knew that they were in grave danger of crashing into the side of some lofty peak. They were in a region of tall mountains, and some high summit might easily loom up before them.

For the next few minutes the youths’ hearts were in their mouths. They knew that Karl was an excellent pilot, but they also knew that he could do nothing if sudden tragedy might come upon them.

“What’s that?” cried Bob quickly. He had seen something that looked like a huge black mass directly before them.

Joe sat on the edge of his seat, expecting every moment to feel a terrible crash and then.... For the first time he wondered what death was like.

Cries of relief came from the youths as they saw that instead of crashing into the black mass, they were passing through it.

“As if a million pounds were lifted off my back,” gasped Joe. “I thought we were goners sure.”

“Would be if that were a mountain,” Bob said. “As it is, we’re no worse off than before. It’s a lot darker, though.”

Karl sought to pass out of the cloud by gaining altitude, but he soon saw that this was useless. Still, he thought it best to fly higher. There was a limit to the height he could safely reach, however, for neither himself nor the youths were using oxygen, and the high rare air was not sufficient to supply enough necessary to the human body.

“I’ll have to trust to luck, I guess,” he said through the telephone. “We may make it all right.”

“Karl didn’t say that any too hopefully,” remarked Joe. “Do you suppose he really fears disaster?”

“It seems like it.” Bob was terribly worried. He did not have much hope of getting out unharmed.

Then suddenly the air travelers received a surprise. The cloud that had a few seconds before been so heavy and dense quickly thinned out until it passed from view. Once more the blue sky was visible.

The explorers could hardly believe their eyes. Had they actually emerged from what seemed like certain disaster? It was some time before anyone spoke.

“What do you think of that one?” Karl Sutman’s voice was the first to break the silence. “Couldn’t have been much worse suspense, could there?”

“We didn’t see that we had much chance,” said Joe gravely. “And when we saw that black mass——”

“We’re out of it now, though,” the aviator said. “So why not dismiss it from your mind?”

He was put out to think that the monoplane was several miles off its course, but he refused to let that worry him, since they had had such a miraculous escape.

It did not take long, however, to make up for the lost time, for the young pilot well exceeded the hundred-and-fifty-mile-an-hour cruising speed of the monoplane.

As best he could he kept the machine as near the mountain tops as was safe, so as to make it unnecessary to use oxygen. Getting out the masks and tanks would require much time, and that was what they did not want to spare.

“There’s Mount Panta,” observed Joe, his eyes on a massive peak. “Why can’t we stop and see the archÆologists—for only a few minutes, I mean? I suppose they’re still looking for Inca ruins in this region, aren’t they?”

“Yes and no,” laughed Karl. “I mean this: they’re still searching for ruins, all right, but not in this part of the Andes. I stopped to see them just before I flew after you fellows, and they told me they were going to leave for another section over to the east.”

“Wish we could have got in touch with them,” said Bob. “We have information about Inca secrets that would make them jump up and down with joy. Maybe we can tell them later, though.”

A half-hour of flying from Mount Panta brought them within sight of the Comberciato River, along whose banks somewhere the youths’ fathers and Mr. Wallace were staying.

Suddenly Bob and Joe cried out in delight.

“Dad! Mr. Lewis! Mr. Wallace!” said Bob happily.