“No you didn’t,” replied the doctor. “It was your imagination that caused you to think you saw him fall. He was probably on the ledge beyond the cataract and staggered as he stepped from the plank.”

This was the true explanation, and takes us back to Hal when he was entrapped. He saw what his companion had done and attempted to reassure him that no serious damage, beyond the loss of the plank, had resulted; but Frank darted away in terror almost instantly.

Hal watched the fleeing boy with puzzled amusement at first. He could not understand why he should have run away so hurriedly. He did not know that Frank believed he had killed his friend, but supposed the impetuous lad was hastening away for assistance. However, it seemed strange that he should not have tried to tell Hal his intentions.

Having no fear as to the outcome of his adventure, Hal began to look about him. But the cave was dark, except close to the roaring water, and he was able to see but little. He was afraid to venture far back lest he step into a pit or over an underground precipice. So he decided to wait where he was until help arrived.

Presently his eyes fell again on the supposed bag of souvenirs, and he stooped over and picked it up. Yes, there was no mistake about it; the object was a bag of soft leather and contained half a peck, seemingly of small stones or quartz. The string, run through a dozen eyes near the opening, was tied, and as it was too dark to see, he did not open it. Help would come to him in a few minutes and he would turn the bag over to Dr. Byrd for further inspection.

But help did not come in a few minutes. Half an hour passed and Hal began to wonder a little. He had reasoned out an explanation of Frank’s sudden departure, so that had ceased to puzzle him. Frank was very impetuous, and undoubtedly had realized at once that it would be useless, on account of the noise of the waterfall, to attempt to talk with the prisoner, so he must have decided instantly that the only thing for him to do was to run for assistance before it became too dark.

But as the shades of the cañon grew heavy and no rescuers appeared, Hal became uneasy. Probably an hour had elapsed since he was trapped in this place, and he was becoming alarmed. What could have happened to Frank? Had he fallen into the river and—no, that could not be. Hal had watched him until he passed the deep part and sat down near the fording place to pull off his shoes and stockings. Frank had crossed the river, no doubt.

Another half hour elapsed and the prisoner was ready to give up hope for the night. Something had happened to prevent Frank from carrying the news to Mr. Porter, or else it was deemed too dark to attempt a rescue at once. The west shore was pretty steep and a single misstep in the dark might plunge one into the water or onto the rocks, ten, fifteen or twenty feet below. Possibly some one had been sent back to the school for lanterns.

Several times he wished he had some matches in order that he might explore the cave and examine the contents of the leather bag, but Dr. Byrd never permitted his boys to carry any. The buildings of the school were lighted by a small electric plant connected with the shops, and they were heated with steam pipes and radiators, so that there was little call for the use of matches on the part of anybody at the school. Moreover, the doctor had absolutely forbidden the use of cigarettes at Lakefarm, and matches are very necessary to the habit.

The waterfall was almost as effective as a stone wall would have been in shutting from view the light of the moon in the cañon. However, from the point where he had crossed over on the plank he could look out and see dimly the shadowy contour of the mountain. Then, gazing upward at an angle, he could see a few stars shining dimly.