About the middle of the forenoon Pompey curled up on a pallet in one corner of the room, and went to sleep. There was nothing in particular to do, and it seemed rather a sensible way of spending the time. Dean, however, felt too anxious to follow his example.

It occurred to him that it would be a good time for him to gratify his curiosity by examining the cavern in which he was immured, and devise, if possible, some method of escape. First he went up close to Pompey, and examined him carefully to see whether he was really asleep, or only shamming. But the negro's deep breathing soon satisfied him that there was no sham about his slumber. So Dean felt at liberty to begin his exploration.

He went back to the entrance, which he knew by the staircase he had descended with Kirby and Dan. He mounted to the top, and found his way barred by a trap-door which he tried, but unsuccessfully, to raise. It appeared to be secured by a lock, and, not having the key, there was no hope of escape. He gazed ruefully at this door, which shut him out from liberty.

"I wonder if there is any other way out of the cave," he asked himself.

It didn't seem probable, but it was of course possible, and worth while to investigate. If there were it would be at the other end, no doubt.

He retraced his steps, and found Pompey still fast asleep, and utterly unconscious of the movements of the prisoner under his charge.

Dean took a lamp and went farther into the cave. There seemed to be a series of excavations, connected by narrow passages. In one of these was a large box, constructed like a sailor's chest. It occurred to him that it might belong to Pompey, and be used by him to contain his clothing. But a little thought suggested that the negro was not likely to have a large stock of clothes. Probably the suit he had on was about all he possessed. What, then, did the chest contain?

At each end was a handle. Dean took hold of one and tried to lift the chest. But he found it very heavy, much heavier than it would have been had it contained clothing.

He rose to his feet and eyed it with curiosity. There was nothing elaborate about the lock, and it struck Dean that a key which he had in his pocket might possibly unlock it. Upon the impulse of the moment he kneeled down and inserted it in the lock.

Very much to his surprise, and indeed it did seem an extraordinary chance, for it was the only key he had, it proved to fit the lock. He turned it, and raised the lid. The sight dazzled him.

Before him lay piles of gold and silver coins, and a package of bank bills. This cave was evidently the store house of an organized band of robbers, and the chest might be considered their treasury.

"I wonder if this is real," thought Dean. "It seems like a scene in the Arabian Nights."

It did indeed seem strange that this far off nook of Colorado should be the rendezvous and treasure house of a band so widely scattered that the captain was a quiet citizen of a small town in the State of New York, nearly two thousand miles away.

How improbable it would have seemed to the Citizens of Waterford, among whom Squire Bates moved, living in outward seeming the life of any other respectable and law abiding citizen! This was the Waterford mystery, which by a series of remarkable adventures it had fallen to Dean to solve.

He locked the chest, fearing that Pompey might suddenly awake, and, following, discover what he was about. He wanted some time to think over this strange discovery, and consider what to do. To be sure, there seemed little chance of his doing anything except to remain where he was, a subterranean prisoner.

Dean felt more than ever a desire to leave the cave, but the prospect was not encouraging. Why he was kept a prisoner he could guess. He knew too much of the band, and especially of their leader, and he was considered dangerous. His imprisonment might be a prolonged one, and Dean felt that this would be intolerable.

It was in a very sober frame that he returned to the room where Pompey was still sleeping. An hour later the negro awoke and stretched himself.

"Have I been asleep long, young massa?" he asked.

"Two or three hours, I should think, Pompey."

"Dat's strange! I only just closed my eyes for a minute, and I done forgot myself."

"You might as well go to sleep. There's nothing else to do."

"I must get some dinner, honey. Don't you feel hungry?"

"I might eat something," said Dean listlessly.

Pompey bustled round, and prepared a lunch, to which Dean, homesick as he was, did not fail to do justice. It takes a great deal to spoil the appetite of a growing boy.

After the noon repast Dean sat down. He was beginning to find the monotony intolerable.

"Have you got any books down here, Pompey?" he asked.

Pompey shook his head.

"No use for books, young massa. I can't read."

"But I can."

"Perhaps Massa Kirby will bring you some if you ask him."

Dean did not care to ask any favor of Kirby. Moreover he knew that that gentleman was not particularly literary, and doubted if he was in a position to grant the request.

By way of beguiling the time he took out his harmonica in an absent mood, and began to play "Old Folks at Home."

Instantly Pompey was on the alert. His eyes brightened, and he fixed them in rapture upon the young player.

"What's dat, young massa?" he asked.

"That's a harmonica."

"You do play beau'ful, young massa."

"Thank you, Pompey, I am glad you like it."

"Play some more," entreated Pompey.

Dean complied with the negro's request, partly because he was obliging, partly because it helped to fill up the time. He could scarcely forbear laughing to see Pompey rocking to and fro with his mouth open, drinking in the melodious strains.

Nature had given Pompey a rapt appreciation of music, and he began to croon a vocal accompaniment to the instrument.

"Who learn you to play, young massa?" he asked.

"I taught myself. It isn't hard."

"Dat's because your white. A poor nigger like me couldn't learn," said Pompey half inquiringly.

"Oh yes, you could. I see you have an ear for music. Would you like to try?"

"If you would let me."

Dean handed the negro the harmonica, and gave him the necessary directions. In the course of half an hour he was able to play through "Old Folks at Home," with substantial accuracy.

"I wish I had a harmonicum," said Pompey wistfully. "It would make old Pompey happy."

An idea came into Dean's head—a wild, perhaps an impracticable idea, but he resolved to carry it out, if possible.

"Pompey," he said, "I'll give you the harmonica if you'll let me out of the cave."

Pompey rolled his eyes in affright.

"Couldn't do it no how, young massa," he said. "Massa Kirby would kill me."

"He'd think I got away when you were asleep, Pompey. Come, I'll show you two or three more tunes on the instrument, and you can learn others yourself."

"I don't dare to, young massa," said Pompey, but there was a suspicion of indecision in his voice.

"Very well, then, give me back the harmonica. I will never play any more upon it."

"Oh, young massa!"

"I mean what I say, Pompey"—and Dean put the harmonica in his pocket.

Pompey eyed him with a troubled look. He was evidently weighing the matter in his mind.

"If I thought Massa Kirby wouldn't kill me," he said reflectively.

Dean upon this redoubled his persuasions. He played another tune on the harmonica—"Sweet Home"—with variations, and this completed the conquest of his sable custodian.

"I'll do it, young massa," said Pompey, hoarsely. "Give me the harmonicum, and I'll take the risk."

Dean did not want to give him time for reflection. He seized his hat, and handed Pompey the instrument.

The negro guided him, not to the front entrance which he already knew, but to a back exit which he had overlooked. Here there was a door skillfully concealed on the outside. Pompey drew out a key, opened it, and with infinite relief Dean again saw the sunshine and breathed the air of freedom.

"Good-bye, Pompey!" he said. "I thank you with all my heart."

"If Massa Kirby cotch you, don't you tell him I let you go," said Pompey, hoarsely.

"No, I won't, Pompey, but I don't mean to let him catch me."

The door closed behind him, and Dean paused to consider what course to take. He must at all hazards avoid falling in with Kirby and Dan.

"That harmonica is worth its weight in gold!" thought Dean, gratefully. "It is a regular talisman."