BOB looked at his father in surprise.

“What do you mean?” he asked.

“Simply that no one is there to drive away now,” was the reply. “We have captured all of the Arabs—even the two thieves who stole Fekmah’s map. And I might add that we have located the hidden treasure.”

“What! You’ve been there?”

“No, but we’ve seen the cave in which it is. In fact, it is possible to see it from here.”

Mr. Holton took out his binoculars and handed them to his son.

“Look away over there,” the naturalist said, pointing to a distant wall of rock that was many hundred feet high. “That small shelf on the side of the cliff is an opening into the cave in which are the hidden riches.”

Bob scanned the landscape ahead. Then he cried out in surprise and amazement.

“A cave away up in that cliff? Seems impossible. How can you get to it?”

“Must be an entrance on the other side,” Dr. Kirshner replied. “Fekmah’s map no doubt points it out. Whether he remembered to put it on the duplicate after the original was stolen, we have yet to see. Where is he now?”

“Who, Fekmah? I left him at camp this morning.”

“Let’s go there now.”

First, however, Dr. Kirshner engaged in conversation with the Tuaregs in their own language. He told them, among other things, of how grateful he and the other former prisoners were for their help in releasing them from the clutches of the Arabs.

The natives were very courteous and friendly, inviting the archÆologist to their village. He returned that he would be delighted to visit them, and concluded by saying that they would be given a reward for their generous services.

“Now let’s get out of here,” he said, turning to his friends. “I’m particularly anxious to get back to camp and see Fekmah. I wonder if any misfortune could have come upon him and our camels.”

The Americans, Tuaregs, and Arab captives left the cave behind and trudged down the mountainside. But before they did so, they carried out the food supply that had been in the cave for the prisoners and their guards. It consisted of simple native food, but was welcomed by the Americans and Tishmak.

“There is much more in the cave where the hidden treasure is,” remarked Joe, as he walked beside his chum, who was leading his camel. “We won’t need to worry about not having enough to eat for many weeks.”

“Doubt if we’ll stay here that much longer,” Bob said. “But I imagine it’ll come in handy all right.”

The Arabs were ordered to walk in front of the Americans and Tishmak. The Tuaregs rode on to their village, after asking their newly made friends to visit them the next morning.

It required several hours for the explorers and their captives to get back to camp, going on foot as they did. But when they finally came within sight of the tent and camels, all gave sighs of relief.

Fekmah came running out to meet them, his face showing an intense thankfulness at again seeing his American friends and Tishmak alive and apparently none the worse for their experience.

“So Bob got you from Arab demons,” he muttered and then added: “I knew he would do it.”

Nothing would satisfy him but a complete detailed account of their experiences, and it was Mr. Lewis who related all of the happenings since they had last left camp.

“Howard [Mr. Holton] and Tishmak and I were sure greatly relieved when our captors took us to the cave where Joe and Dr. Kirshner were being held,” Mr. Lewis finished. “Funny, but we had not dreamed of them being prisoners.”

“And I see you’ve brought the rascals with you,” observed Fekmah. “What are we going to do with them?”

“I’m sure we’ve all been thinking about that,” Dr. Kirshner returned. “There are no police so far south as this, and we can’t very well take them with us back to Wargla. I wonder how it would be to take them to an oasis fifty miles or so from here and leave them? There would be no danger of them starving, because dates and water would furnish food. And they couldn’t get away without camels.”

“Sounds all right,” Mr. Holton said. “Do you know where there is such an oasis?”

“No, but I’m sure our Tuareg friends do. I’ll ask them in the morning. Until then we’ll have to keep our eyes on these Arabs. It might be well to tie them up.”

This was thought good advice, and the captives were bound together so tightly that they could not escape.

The remainder of that day passed idly, and the explorers retired shortly after the evening meal.

“But we must be up early in the morning,” Mr. Holton told them. “We have a big day before us.”

They all slept the sleep of exhaustion and did not awaken as early as they had intended.

Breakfast over, Dr. Kirshner and Bob got on their camels and started for the Tuareg village. The others put in a request to go also, but the archÆologist stoutly refused, saying that no time must be wasted.

“We only want to make arrangements to take these Arab crooks to an oasis and leave them,” he said. “If more of you go, it will necessarily keep us longer.”

It did not take the two long to get to the natives’ village. The chieftain at once came out to meet the newcomers, and Bob introduced Dr. Kirshner to them.

After a few casual remarks the scientist got to the point. He told the natives of his desire to banish the Arabs to an oasis, if any were near. He also asked if enough camels could be borrowed to take the crooks there.

The chieftain at once replied that he knew of an oasis a half-day’s journey from the village, and that he would gladly let them have the camels.

“Fine!” Dr. Kirshner said in the native tongue. “We’ll go there at once.”

The chieftain insisted upon leading them to the oasis, for, he said, they could not find it alone.

Dr. Kirshner consented, and the head native at once herded enough camels to take the prisoners away. Then the Americans and the Tuareg chieftain started for the explorers’ camp to get the Arabs.

“Be glad when this job’s over,” remarked Bob, as they rode toward camp. “I’m anxious to see the hidden treasure.”

They arrived at camp and placed each Arab on a dromedary. After preparing a lunch to last them until they would return, Dr. Kirshner, Bob, and the Tuareg chieftain began the journey to the oasis, riding behind the prisoners and guarding them closely.

The oasis was about forty miles away, situated on a barren sand plain surrounded by mountains. The Tuareg explained that there was no other well near and that the prisoners would be forced to stay there for an indefinite period, for no caravans passed along that way.

In order to get to the place it was necessary to go through the mountains, and traveling was not any too easy. But they rode with a determination and finally arrived at the oasis.

The Arabs were commanded to dismount and walk forward. Then, after filling their canteens with water, the Americans and the Tuaregs started the return journey, herding the dromedaries ahead of them.

“Now that that’s over, maybe we can rest easy,” said Dr. Kirshner. “Those Arabs can’t get away because of not having camels, and the monotony will punish them greatly.”

Bob, the scientist, and the Tuareg made good time that afternoon, arriving at the explorers’ camp just before sundown. The chieftain lost no time in getting back to his village, after being thanked warmly for his services.

“We’ll see that those Tuaregs get a reward,” said Mr. Holton. “Just as soon as we get to the hidden treasure we’ll give it to them.”

The natives had not been told of the cave of riches, however, for fear that their age-old desire to raid might get the better of them.

Very early the next morning the explorers got their belongings placed on the dromedaries and started out for the cave of treasure. Although it would mean only a few hours’ journey, they were extremely impatient.

“Wonder if those Arabs carried any of the riches away?” asked Bob, as they rode toward the high wall of rock, in the side of which was the cave.

“No,” Mr. Holton returned. “They hadn’t started yet. Were just looking over everything. At least that’s what our guards told us. It seemed that they intended to carry the stuff out in a day or two.”

“Wanted to catalog everything first, huh?” asked Bob. “Well, it’s a good thing we stopped them when we did.”

Fekmah found it necessary to consult his duplicate map very frequently, and he wondered if he had remembered to put in all the details accurately.

Finally, after they had passed the tall wall of rock and were following a narrow trail up the mountain on the opposite side of the cliff, Dr. Kirshner turned to Bob.

“You asked the other day how we were to get into the cave,” he said. “Of course it would be impossible to scale that lofty cliff. Fekmah’s map points out a narrow opening in the rock somewhere in this vicinity, and we ought to find it in a very few minutes now.”

He had scarcely uttered the words when Fekmah cried out in delight and pointed to a peculiar rock formation not far ahead.

“There it is,” he declared joyfully. “There is where we enter mountain to get cave of treasure.”

The explorers, led by Fekmah, moved on up to the spot.

“Here’s an opening!” cried Joe, pointing to a small crack that was barely large enough to let them in.

Getting out their flashlights, they followed Fekmah through the crack and into a narrow tunnel. The air was damp and heavy from the breath of ages, but they trudged on through.

After what seemed like hours, the passageway gradually became lighter, and the explorers found themselves in a large cave.

Suddenly Joe stumbled and fell, unable to catch himself.

“What’s this!” he mumbled.

Then, as his light was turned to the floor, he gave an exclamation of joy.

“The hidden riches!” he said excitedly. “I’ve found them!”