After reading the doctor’s note, Hal picked up the lantern and swung it around so as to get a wider view of the cave. He was able to see the wall at the other edge of the cataract, but was not sure of the depth of the cavern.

Then he set the lantern down again and searched his pockets until he found a piece of white paper and a pencil. For a few moments he cast about him for a hard, smooth surface on which to lay the paper, but the best he could find was the plain flat handle of his pocketknife. With this on his knee and bending close to the light of the lantern, Hal laboriously inscribed the following:

“I’m all right till morning. I’m going to explore the cave.”

He tied this note to the rake and reached it back to Pepper. Then he waited for the answer he saw the doctor preparing. It came presently and was as follows:

“Be careful and don’t fall into another trap. We’re going back to the other side. Maybe we’ll try to get you before morning.”

Hal saw the two men depart and then turned his attention to the dark depths of the cavern.

The floor was smooth, though irregular. The mouth opening upon the waterfall was about ten feet wide, but the passage narrowed somewhat further in. Here it made a sharp turn to the right, and Hal followed the passage a hundred feet, when he was stopped by a wall of earth and rocks. There was no further exploration to make, for this was the end of the cave.

Hal flashed his lantern all around and above, but could find nothing more of particular interest, except the general formation of the cave. He was not certain that he could see the ceiling. At one place particularly there seemed to be a black void above.

The right wall of this part of the cave slanted upward like the side of a steep hill. Moreover, this side was jagged and irregular, so that Hal was certain he could climb up some distance. The other side hung over like a huge cliff, slanting at the same angle.

“This looks like a big crevice in the rocks,” mused the boy as he gazed up and around him. “I wish some more of the boys were here with lanterns. I’d like to hunt till I found something worth coming here for. It looks like a shame to have such an adventure as this and find nothing.

“Oh, yes,” he suddenly remembered; “there’s the bag of souvenirs. I haven’t examined them yet. I’ll go back and see what they are.”

So he turned to the mouth of the cave and set the lantern down on the floor, while he stooped over and untied the string around the opening of the leather bag. Pulling it apart, Hal was soon fingering a curious collection of many sorts of stones and quartz, some of which shone brilliantly in the light of the lantern.

“My! they look as if they might be worth a fortune,” exclaimed the boy as he picked up one after another and examined them eagerly, “for Mr. Miles said he wouldn’t take a thousand dollars for them.”

As he had nothing else to do, Hal continued to examine the curios for some time, becoming more and more impressed with their novelty. Some of them evidently had been altered in shape by the hand of man, particularly a few that looked like Indian amulets, and Hal was convinced that the collector had visited some deserted pueblos or cliff houses.

“Dr. Byrd said Mr. Miles had spent some time in the mountains,” he mused: “and I bet he can tell some interesting stories of the places he’s been in. When he gets well enough to be around, I’m going to ask him to tell us all about his adventures. He must have had some with that airship in the mountains.”

Hal’s meditations and his interest in the contents of the leather bag were interrupted finally by the reappearance of lights approaching along the river bank. He drew the string tight around the receptacle and tied it. Then he awaited the approach of his rescuers.

As they came near, he saw that they were bearing two wide planks, one man at either end of each, the leaders carrying the lanterns. Evidently they had decided not to wait until morning before attempting to release the boy from his strange prison.

Finally they reached the flat rock near the waterfall and the two planks were laid across the intervening space between the shore and the cave. Hal adjusted his end of the planks so that they rested firmly; then he picked up the leather bag and his lantern and walked across the bridge.

Without further delay, they turned and walked down the stream again. No attempt was made to discuss the affair until they had forded the river and returned to the stage road near which the automobile had been left. Hal was then the first to speak.

“Where’s Frank?” he inquired.

“We took him back to the school and put him in bed,” replied Mr. Frankland. “Evidently you could see and recognize him from behind the waterfall.”

“Yes,” answered the boy. Then he continued: “It wasn’t his fault that I was trapped behind the fall. It was all an accident. He slipped and hit the board with his foot.”

Hal’s companions were amused at this unconscious charity toward Frank. If there had been light enough they probably would have winked at each other. In his fear of the gallows, the former youthful terrorizer had confessed just how he happened to kick the plank into the waterfall and, as he thought, dropped Hal to a fearful fate.

With little delay, except to crank the machine, they all got into the automobile and soon were bowling along the stage road. As they were leaving the caÑon, Dr. Byrd inquired:

“What kind of place is that cave, Hal?”

The boy gave a brief description of it; then he added:

“It’s a dandy. It isn’t so awfully big, but it’s big enough; and it’s so different from most caves.”

“You didn’t find any rubies or garnets or streaks of gold there, did you?” inquired Mr. Frankland, nudging the boy, who sat beside him in the back seat.

“No, but there might be something of the kind. I wish we could go back with lots of lanterns and examine the place carefully.”

“I think we’ll forget all about that cave for a while at least,” announced the doctor with an air of decision. “It came near proving a fatal discovery, and I feel like waiting until I’ve had time to get over this scare.”

Hal had offered his suggestion rather doubtfully, for he felt that a scolding was due him and Frank for their boldness in crossing the river and continuing their search along the steep shore on the west side. However, the adventure had proved successful, for the lost bag of specimens had been found; so the boy did not feel nearly so much like a culprit as he would have felt in the face of failure.

But the doctor said nothing more that might sound like criticism. He was too thankful for the discovery and rescue of the lost boy for that.

Presently the talk was changed to the bag of specimens. Naturally much wonder was felt because of the place where it had been found. Hal explained his theory that in falling from the aeroplane it had struck a slanting projection of rock and bounded into the cave.

“Of course that’s barely possible,” said Dr. Byrd; “but it’s hardly probable. I can’t get away from the belief that the bag did not break loose in the air.”

“You think it fell to the ground with the aeroplane?” Hal inquired.

“Yes. Why not? I can’t conceive what force could have broken or pulled it loose before the machine hit the ground. Did it just happen to come untied from the strut at that time? Barely possible.”

“How did it get into the cave then?” asked Mr. Porter.

“Somebody put it there if it didn’t fall there,” volunteered Pepper.

“Of course,” said the doctor.

“Somebody might have put it in the cave,” agreed Hal reflectively. “We weren’t the first ones to discover the place.”

“How do you know?” inquired Dr. Byrd quickly.

“By the plank we found in the bushes. It was there for a bridge, that was plain. Somebody’s been using the cave for something.”

Exclamations of surprise greeted this information.

“Did you find anything in the cave that tended to prove your suspicion?” asked Mr. Frankland.

“Nothing except the leather bag.”

Hal hoped that his suggestions would arouse the interest of Dr. Byrd to such an extent that he would decide upon further investigation, but he was disappointed. If the owner of Lakefarm felt any such desire, he failed to express it.

On their arrival at the school, the automobile was run into the garage, and then a general move was made for their bedrooms. While the doctor explained matters to his wife, Hal and the two instructors had gone to bed.

The noise Hal made in entering the dormitory and walking along the hall awakened Bun Bowler, who was sleeping with his brother Frank. Eagerly Bun slipped out of bed and peeped through the slightly opened doorway.

“Oh, they’ve brought Hal back,” he said to himself. “I wonder where they found him.”

Had it been Frank he would have yelled out a congratulation, in spite of the lateness of the hour and the rule requiring quiet in the dormitory, but Byron crept quietly back into the bed. As he crawled over his brother—Frank always insisted on sleeping in front—the latter gave a start and a jerk and cried in a voice of terror:

“I won’t do it any more! I won’t do it any more! I won’t threaten to clout anybody in the jaw—never, never again!”