There was no question about this.

A little delay and the two prisoners would no doubt have passed in their final accounts.

As it was hardly likely that Frank would have been able to have escaped from the plateau.

It was, however, they were safe and there was good reason for self-congratulations. It had been a narrow escape.

The soldiers were looting the stone house of the counterfeiters. Bushels of counterfeit coin was seized and all the tools and dies in use.

It was a big haul, and not for years had so extensive a den as this been discovered.

But Captain Elmo was not satisfied.

The ringleader and indeed nearly all of the gang were at large.

Frank Reade, Jr., was desirous of effecting the capture of Bert Mason, as the villain’s identification was necessary to save the life of Benjamin Astley.

Captain Elmo was presented to Frank Reade, Jr., by Barney and the two men had a lively conversation.

“I have been looking for Mason for a long while!” declared Elmo. “It is lucky we happened to meet, for if I had caught him I should have hung him to the nearest tree, and then your man, Astley, would have remained unidentified.”

“Yet if we do not capture Mason, I fear my man is lost!” said Frank.

“You’re right; he is at large now at least.”

“Yes.”

“But we must capture him. Where do you think he has gone?”

“Come with me and I will answer that question!” said Frank.

The young inventor led the way to the verge of the plateau.

“He went out of sight in this direction,” he said.

“What!” exclaimed the captain, aghast. “You don’t mean to say that he actually leaped over into the valley?”

“I don’t know. I only saw him disappear about here.”

“But I can see no way of climbing down here.”

“Nor I. It may be possible that he committed suicide here, but I doubt it.”

“What then is your opinion?”

“There must be some secret way of getting down the face of the cliff here.”

“Let us examine.”

For some while the two men made a close examination of the vicinity. But this resulted in nothing.

“The mystery is yet unexplained,” declared Captain Elmo.

“So it is,” agreed Frank. “Now I will advance a theory.”

“Pray, do so.”

“Of course you understand the nature of that valley down there and its sandy trail of death?”

“I understand that the bodies of many victims to the peculiar atmosphere of the valley yet lie down there.”

“Yes.”

“And that it is not safe for any person to venture into the place.”

“Quite wrong, sir!”

“What?”

“It is quite safe for anybody to cross that valley.”

The captain looked astonished.

“I fail to comprehend,” he said.

“I will modify my statement,” said Frank, “and affirm that there are times when it is safe to cross the valley.”

“Ah, that is quite as surprising. What time or when is it safe?”

“At night.”

The captain cleared his throat and looked quizzically at Frank.

“Have you tried it?”

“No.”

“Ah! Then do not.”

“To the contrary, I will try it, and prove to you that I mean what I say this very night.”

“Do not do anything rash.”

“What is more, I will capture the counterfeiters for you at the same time if you will follow my directions.”

“What are they?”

“Post soldiers at near intervals all around the valley. The rascals certainly are hiding in some place in the cliffs.”

“Ah! what is their purpose?”

“Escape! They will in the night cross the death valley and get away from us.”

The captain was much impressed with Frank’s statements.

“I have no intention of disputing you, Mr. Reade,” he said, quietly, “or of seeking to know how you get your information.”

“Simply by observing a few natural phenomena in connection with the valley.”

“Ah!”

“I will show you more clearly to-night.”

“Then I will follow your directions to a dot. I suppose that by to-morrow we shall have the counterfeiters all in our power.”

“I think so.”

The captain went back to his men.

He proceeded to follow Frank’s instructions carefully.

Men were placed at intervals along the plateau and with rifle shot completely around the valley.

Unless there was some unknown exit by means of a secret cavern, Frank could not see how the counterfeiters could escape.

The day was spent in overhauling and exploring Mason’s den.

Towards night Frank, with Barney and the trapper, Beaver Bill, went to the verge of the plateau.

Pomp was left with the Steam Horse by the stone house.

Frank’s theory was that the counterfeiters were secreted beneath the cliffs and were waiting simply for night to enable them to find their way across the valley.

But how they had gone down over the edge of the cliff seemed a mystery.

This, however, Beaver Bill soon solved in a curious manner.

The trapper found several stout iron rings imbedded in out of the way crevices of the cliff.

His theory was logical.

“I tell ye, I reckon they had double lengths of lariat passed through these rings,” he declared. “They evidently had this all fired anticipating an attack some time.”

“Begorra, I can see that,” cried Barney, “but howiver did they go down and be afther taking the ropes wid thim?”

“Easy enough, pard,” replied the trapper, “the lariats were doubled an’ by jest untying a knot they could pull the rope down arter ‘em, an’ ye couldn’t foller in the same way.”

There was no doubt but that Beaver Bill had hit the nail on the head.

All accepted this hypothesis as a correct one. But darkness was coming on rapidly now.