URGING his dromedary on to the utmost, the youth was carried over the narrow valley at a pace that ate up the distance surprisingly. In fact, never had he traveled so rapidly on camelback.

When he was several hundred feet away, he glanced back, to see that two of the Arabs were pursuing him desperately. At the start he had put a good distance between himself and his enemies, but now the latter were gaining swiftly. They were more familiar with the country and knew better how to command their camels to move fast.

“If I can only make that little canyon,” the youth thought, bending low so as to lessen the wind resistance.

The canyon was near now, but a hurried look over his shoulder told Bob that the Arabs were near also. If he could only get there!

He lashed the dromedary with a new determination and entered the narrow way between the mountains just as the Arabs passed over a small grove of low shrubs some two hundred feet away.

Bob knew that this was a very short canyon and that there were numerous large rocks and crevices at the opposite end. Perhaps he could successfully evade his pursuers by hiding in one of these openings in the mountainsides.

Sharp jagged crags protruded from all sides of the thread-like passageway between the high walls. It was very dangerous to ride with much speed in such a place, but the chance had to be taken.

He reached the other end of the passage with but a moment to spare. Immediately his dromedary was cut over to the right behind a barrel-like rock. But the youth did not stop there; he wound in and out among the many huge boulders.

At last he came to a stop in a large crevice between two imposing slabs of stone. With every nerve on edge, the young man listened.

“They’re coming!” he thought, getting out his revolver. “But they won’t get me if I can help it!”

But he was in a very secure hideout, and it was unlikely that the Arabs would locate it. Still he realized that they probably knew this region better than did he.

As Bob waited breathlessly, his mind was in a whirl. Who were these Arabs? What did they want? Why had they descended upon the little exploring party so mysteriously? Bob did not know what to make of the situation, but he knew that danger was at hand. What further added to his perplexity was the fact that Arabs did not normally inhabit the Sahara so far south as this.

Suddenly he started, as a thought struck him. Was it—the two thieves who stole Fekmah’s map? Entirely possible, of course.

Then a strange thing happened. As though informed by some unseen power, Bob grasped the whole situation. He saw Dr. Kirshner and Joe in the clutches of the two thieves, being held as prisoners. He visioned his father, Mr. Lewis, and Tishmak riding away under the guard of the Arabs.

“Those thieves did it, then, to keep us away from the hidden treasure,” thought the youth, and he could not have had a more accurate realization.

For some time he listened closely for any sound from the two Arabs who had pursued him. He thought once he heard the footsteps of camels, but was not sure.

What was he to do next? He was now doubly glad that good fortune had enabled him to escape from the would-be captors. If the Arabs had been nomad plunderers, he would probably not have suffered much by remaining with his father and the others. But as it was, there was a possibility of bringing rescue to his friends.

“How am I to do it?” the youth mused, trying to remain calm.

Suddenly the far-away noise of footsteps came to his ears, and he knew that the two Arabs who had followed him had given up and were abandoning the chase to join their friends back in the valley.

After several minutes of waiting, Bob got off his camel and tethered the brute to a small protruding rock. Then he walked over to some distance beyond the mountain near which he had been hiding.

He glanced up to the top of the peak and saw that it was unusually high. The sides stretched almost straight up.

“If I could only get to the top of some tall mountain,” Bob thought, his eyes scanning the landscape. “Then I might be able to see where Dad and the others will be taken.”

The peak before him offered no footholds and therefore could not possibly be scaled. He looked about for other sky-piercing hills. At last his eyes fell on one about a hundred yards away, and he resolved to inspect it.

“Looks like there might be a chance there,” the youth thought and then walked over and untied his dromedary.

He rode over to the mountain, every step bringing new hope. The peak, rocky as it was, was rather gradual and not straight up, as were many others in the vicinity.

Once more the camel was tied by the rocky side, and Bob moved over to gaze up to the top. The dizzy height almost took his breath away. But he saw at once that it would be possible to climb to the very summit of this imposing peak of rock.

Bracing himself to the task that was before him, Bob began the dangerous ascent, slowly, at first, and then climbing faster. It was exhausting, fear-inspiring, but he went bravely up. There was no option in this case. He must observe where his father and the others would be taken by their Arab captors.

“If I can only get up in time,” the young man thought, as he sought out a means to ascend a five-foot plate of smooth stone that was directly above him.

To do this, it was necessary to edge on around the mountainside until he came to a rough, gradual section. Then climbing became comparatively easy.

Once, when he was but a third of the way up, he glanced back over his shoulder to the ground below and almost lost his balance. But he caught himself with a quick motion, and after resting a moment from the terrific strain, continued the climb. That glance to the ground had revealed that he was several hundred feet up. How easy it would be to slip backwards!

Another hundred feet and he found himself on a wide shelf, which seemed to encircle the peak. A short rest was taken here, and in the end he felt much better for it.

“Wonder if I can get down from here?” the boy mused, again taking up the climb. “I’ll find some way, though,” was his conclusion.

For a few more hundred feet the way was very gradual, with many rocks of different sizes affording footholds. But as he came to a sharp break in the side of the mountain, the lofty pointed crag shaped up straighter and more jagged. Once he thought he had gone as far as possible, but finally managed to get to the brink of a slab that had threatened to hinder his progress.

“On to the top,” he thought, bringing his foot up another notch with difficulty.

At last, panting and perspiring, he ascended the last stretch and took his position on the flat surface of a platform-like formation. Then he turned to look below.

A cry of astonishment came from his lips as he saw that he was hundreds and hundreds of feet in the air. Far, far below, he could dimly make out his dromedary by the outermost side of the mountain. The beast seemed no larger than an ant.

“I wonder if Dad and the others can be seen,” he mused, turning his gaze in the opposite direction.

“Yes!” he muttered excitedly. “There they are.”

He had caught sight of his father and friends being led up the valley by their Arab captors. The camels on which they rode seemed only crawling, so small did they appear.

As usual, his binoculars were strapped over his shoulder, and he took them out to get a closer view. Through them he could see the worried expressions on his friends’ faces, and the surly grins of the Arabs.

There was a sort of narrow ledge that passed up the little valley and around the mountain. It was up this that the captives were being led.

“There’s probably a hideout somewhere around here,” the youth thought, shifting his eyes from the camel procession to the rugged country ahead.

From his lofty perch it might be possible to get a glimpse of the hidden cave in which were the riches. Bob scanned the landscape about him but finally gave up and again followed the movements of his friends and the Arabs.

“If it’s anywhere around here, it’s concealed from view,” he thought.

The youth was crouching low behind a flat shelf of rock, so as to be invisible to the Arabs if they should happen to look up in that direction. He knew that their seeing him would spell his doom.

As Bob watched the line of camels and their riders, it seemed that they were making no time at all; yet he knew that they were winding around the mountain as fast as possible.

Up, up, up they went, but always in sight. Bob noticed that they were gradually moving away from him, and he wondered if he would be able to follow their movements to the end.

“If I can’t, I’ll have to change peaks,” he thought, although he realized that this would be difficult and dangerous.

The Arabs and their captives were now nearing a high wall of rock that would prevent them from being seen. But it would be for only a short time—if they did not stop opposite it.

After what seemed like hours to Bob, they emerged again into view, this time at the brink of a high cliff.

“Hope they don’t step off of there,” the youth breathed, his heart in his mouth.

At last, just as the sun was beginning to sink behind the distant peaks, the camels and their riders came to a stop at an opening in a mountainside that evidently led into a cave.

Hardly able to hold the binoculars steady, Bob watched breathlessly, almost expecting to catch sight of Joe and Dr. Kirshner. But those individuals did not make an appearance. Bob did not doubt, however, that they were in the cave.

A moment later, captors and captives dismounted from their dromedaries and walked through the opening out of sight.

Bob waited silently for another half-hour, thinking that it might be possible that this was only a temporary prison. But when at the end of that time no one had left the cave, he was convinced that this was a permanent hideout.

“Now I suppose it’s up to me to get down from here right away,” Bob thought, gliding silently off the shelf and onto a narrow ridge that was directly below.

Carefully he felt his way down with great difficulty. As he had surmised, the descent would prove much harder than the ascent.

Once his heart sank, as he saw that a five-foot wall of stone was directly below him. But then he suddenly remembered that a little to his right there were protruding rocks that would offer footholds. He edged around, and in a short time was again climbing steadily down.

The minutes passed. When he was a third of the way to the bottom, darkness began to fall rapidly. He realized that he could not get to the base of the peak before pitch darkness would envelop him.

“But I’ve got to keep going down,” he told himself, frantically feeling his way among the rocks.

For the past five minutes he had been getting drowsy, sleepy. The day’s strain was beginning to tell on him. With an effort he kept himself awake. He knew the grim consequences if he should suddenly fall asleep while making the dangerous descent of the peak.

He was half of the way down; now two thirds. But a few more hundred feet remained, and he braced himself and continued his slow, careful movement.

“Not much more now,” he observed, glancing down. “Ought to make it in a few more minutes.”

Long before, darkness had come upon him, making the frequent use of his small flashlight necessary. Even then it was a hard task.

“Must be almost to the bottom,” he thought, when another fifteen minutes had passed.

He flashed the light downward and saw that fifty feet still remained. Again he bent his efforts upon the descent that was still before him, and in no time had covered most of the distance.

But just when he prepared to use his flashlight, a small rock gave way from under his left foot. He tried vainly to catch hold of a sharp crag, and then felt himself falling!