Browning was determined, and it was not long before he had worked the others into a state of excitement over it. Without waiting for breakfast, they sprang into the boat and rowed ashore.

"I saw some tools in the sheds at the end of the railroad," said Bruce. "We will secure them."

The path was taken, and they passed through the old quarry and down the track to the sheds. There they found a pick and spade. With those in their possession, they hastened to the black glade in which lay the grave.

For once in his life Bruce Browning was filled with energy—he was aroused. But even as he reached the grave, he halted suddenly, his hand uplifted, hoarsely gasping:

"Listen!"

The boys were silent.

"Help!"

It was a smothered cry, and it seemed to come from the ground at their feet. It made the hair of the Dutch boy stand and his teeth chatter. It astonished and amazed them all.

"Help!"

Again that smothered cry seemed to come from the grave. What did it mean?

"Use the pick, Hodge!" hoarsely commanded Browning. "We will soon open it up. Go at it lively!"

Bart obeyed, and the ground gave back a strange, hollow sound as he struck his pick into it. Browning shoveled away the dirt, having torn off his coat to work with greater ease.

Soon something of a hole had been made in the mound.

All at once, with a cry of horror, Bart started back, pointing down into the hole they had made.

"Look!" he gasped. "That ring—that hand! It is Frank Merriwell's hand!"

And there before them they saw a human hand that seemed to be thrust up through the ground.

Hans began to pray.

The hand moved—it clawed desperately at the ground!

"It is Frank!" Diamond almost screamed. "He is down there! He has been buried alive! Dig, fellows—dig! But be careful not to hurt him!"

At that moment the ground caved in at their feet, and up out of it rose the dirt-covered head of Frank Merriwell. He rubbed the dirt out of his eyes, and then he cheerfully observed:

"Good-morning, fellows! It seems to be a pleasant morning outside, but it's a trifle close inside. If you will take hold and pull me out, I'll be much obliged."

They clutched him—they dragged him to the surface. Behind him lay a deep, dark hole that was not filled by the earth that had caved in.

"Well, of all things wonderful!" grunted Browning. "Never knew anything like this before—never heard of anything like this! I believe I am still dreaming!"

"Frank, are you hurt?" asked Diamond.

"Not much," answered Merry. "They trapped me without much trouble. I didn't have a chance to get hurt."

"But to be buried under the ground—to be in a grave!"

"Eh? A grave? Why, Great Scott! It is the grave—and the stone with my name on it! This is the spot where I was caught. I was standing right here. A man dropped down out of this tree and struck on my shoulders. He laid me out, and it wasn't hard to tie me up. Then I was towed away under ground, and a guard was placed over me. It's a close little hole down there, but the guard left me after he had watched till he was tired, and then I finally managed to get free, and I tried to dig out where they had closed up what once was the mouth of the cave."

"What's that?" asked Hodge. "A cave?"

"Exactly; and there was an opening into it here at one time. They closed it up and made this fake grave over the spot. That's just what they did."

"But your voice—we could hear it."

"Look at this headstone. There is a hole straight down through it. Below there is a tube that runs down into the cave. Anyone at the lower end of the tube can speak so they can be heard here. That is how those mysterious whispers reached our ears. Oh, it is a great scheme! It made the place seem haunted."

"But where is the other opening to the cave?"

"It must be near here, though I was blindfolded when I was taken in. Mr. Cooler was in the game. He came up suddenly a long, long time ago. Talked with the chap who was guarding me. Said he had been forced to dodge you chaps."

"That's when he gave us the slip," said Diamond. "I'd like to see the little whelp again!"

"Your wish shall be gratified," said a familiar voice, and Mr. Cooler walked into the glade, followed by three other men, all dressed in black. "I am here!"

"It's the gang!" cried Diamond. "We'll have to fight for it, fellows!"

"Don't fight," advised the man in gray, laughing. "It isn't necessary. We are not the gang, but we have the gang nicely corralled. You have known me as Caleb Cooler, but I am, in fact, Dustin Douglass, of the secret service. These gentlemen with me are deputies, and we have just captured a gang of counterfeiters who have been making all sorts of trouble for the government. If you think I am lying, young gentlemen, I will show you my credentials. I managed to get in with the gang myself by pretending to be a skillful shover of the queer, and that is why I have been seen with some of them. Last night my deputies came onto the island in a boat, and this morning we raked in all of the gang. We have them nicely ironed over at the old boarding house, where one of my men is watching over them. Among them, Mr. Merriwell, are your friends, Hicks and Wiley. Somehow they think you were concerned in their undoing, and they have expressed sincere regrets that they did not do you up, instead of capturing you and stowing you here in the old cave. The chap who was watching you came over to get his breakfast this morning, and now he is ironed with the others. There are four in all.

"I trust you will pardon me for the deception, young gentlemen," smiled the little secret service officer. "Had to do it, you know. Just came over to set Mr. Merriwell at liberty, but I see you are here ahead of me."

Bruce Browning leaned against a tree, looking tired and unnerved.

"This is too much for me!" he muttered. "I'm sure to go into brain fever! I can't comprehend it all."

Nor could the others just then, but every word the little man had spoken proved true. He showed them the skillfully concealed entrance to the cave, which was sometimes used in which to hide the bogus money. They understood how he had been able to give them the slip in such a remarkable manner.

Then all went over to the old boarding house, where the boys inspected the prisoners. Dan Hicks glared at Frank and cursed him, snarling:

"All I regret is that I didn't cut your throat!"

Beneath the building was a room the boys had not discovered, and there the "queer" had been made.

At last the mystery of the island was solved, and Frank Merriwell was satisfied. But the boys had been furnished with a topic for conversation and discussion that would be interesting for a long time to come.

And Frank was well satisfied to leave Devil Island at last.