As the three boys, for Dick Donovan brought up the rear, sprang up the gangway steps the burly figure of a sailor suddenly blocked their way.

“You kids keep out of this,” he admonished, and tried to push Jack back.

The boy’s fist shot out and the sailor, caught fairly on the point of the chin, fell in a sprawling heap. Jumping over his prostrate form, as he lay there swearing and trying to regain his feet. Jack and his companions gained the deck.

The first thing their eyes fell upon was Mr. Chadwick struggling in the arms of several sailors. Jack reached the deck just in time to see a noose thrown over his father’s head, making him a helpless captive as it was swiftly drawn down and pulled tight about his arms.

“Let my father go!” shouted Jack angrily, springing forward.

The bristly-moustached man stood in his way. As the boy rushed forward the man thrust out his foot and Jack fell in a heap. In an instant the sailor pounced on him. But Tom, with a shout, pitched upon Jack’s captor. In a flash they were rolling all over the deck.

Jack regained his feet as the heavy form of his captor was removed. Dick Donovan was at his side.

“I’m with you, by Barataria,—I’m with you!” he cried, throwing himself into an attitude of defense as several men ran toward them. Tom had by this time managed to throw off the man whom he had attacked and, springing to his feet, he joined his comrades. The three boys, their backs to a deck house, faced the crew of the yacht without flinching; but their faces had grown deadly pale. Mr. Chadwick had been dragged off and was not to be seen.

The bristly-moustached man got to his feet and glowered at the boys menacingly. Under one of his eyes, so Jack noted with satisfaction, was a rapidly-spreading, plum-colored bruise.

“Now see here, you kids,” he barked out, “it ain’t a bit of good, your putting up a scrap. Your dad tried it and it took a bullet to stop him.”

“You rascal! You wounded my father?” shouted Jack, rushing at him, completely carried away by anger.

But he had not advanced a foot before he was seized by a dozen of the crew who, despite all his struggles, held him fast.

“You see it ain’t a bit of use, your kicking,” went on the man, vindictively. “This yacht carries a crew of twenty men and they’ll all do just as I tell ‘em to. Now that you know what you’re up against, I’ll explain a few things to you just to show you that there’s nothing you can do against my wishes.”

Despite their indignation, the boys listened eagerly for what was to come. Tom and Dick still held their attitudes of defense. Poor Jack was too effectively held to do anything but submit, with what grace he could.

“Them guns you heard was fired by the Professor’s orders. He figured there was a bunch of life savers ashore who’d come out and clap us all in irons for mutiny. We rushed him and finally he saw it was no go and gave in. He’s a prisoner in his cabin now.

“If you and your dad hadn’t come butting in in that contraption of yours we’d have gone on our voyage all peaceable; but you interfered, and now you’ve got to pay for it. If we let you go ashore you’d get the gov’ment after us and we’d get in hot water. As it is, we’ll just lock you up till we make up our minds what to do with you, and then we’ll dispense with you someway.”

“Is my father hurt?” demanded Jack.

“No, he’s all right and will be all right as long as he keeps quiet. I fired a shot at him to keep him quiet, scare him like. That’s all. You can take ‘em below, men, an’ then we’ll keep on our course.”

“But our ship!” cried Jack, anxiously. “What’s going to become of that?”

“Oh, that blamed contraption? Well, that can just as well go to the bottom as not, I guess. Take ‘em away, you fellows.”

Jack, half crazed at the last words of the rascal, was dragged helplessly off. Tom and Dick made a feeble show of resistance, but they, too, were speedily captured and hauled across the deck after him. Unarmed as they were, they had no chance of putting up any fight. And so, within an hour after they had set out to answer the call for assistance, they found themselves prisoners and their Wondership doomed to destruction. No wonder that their hearts felt like lead as their captors roughly shoved and pulled them along.

In this way they were propelled down a flight of steps leading, as soon became apparent, into the saloon of the yacht. From this chamber there opened off several smaller doors. One of these was open and through this and into a small cabin the boys were roughly thrust. Then the men who had made them captive went off without a word, first locking the door behind them on the outside.

The boys looked miserably at each other as the door clicked.

“Prisoners!” exclaimed Jack.

“And the Wondership to be cast away,” cried Tom despairingly, sinking down on the edge of a bunk. “There’s all our work and money gone for nothing,” he added bitterly.

Dick Donovan said nothing. He felt that of them all he was the only one who had no right to say anything. He was there by his own fault solely, and the freckle-faced boy felt that it would have been an impertinence on his part to have made any complaint.

“Well, this is a fine fix,” exclaimed Tom at length, after a long silence, during which they had heard a trampling of feet on deck but had noticed no vibration to show that the yacht was in motion.

“Yes; and that there is so far no explanation for our treatment doesn’t make it any better,” spoke up Jack wretchedly. “It’s the thought of the Wondership being cast loose that makes me feel worst, though.”

“Same here,” muttered Tom dismally; “but can you form any idea as to why we’re being treated in this way?”

Jack shook his head.

“It’s all a Chinese puzzle to me,” he said. “Of course, that ruffian on deck hinted that there had been a mutiny of some sort, and that between the time that we answered the signal guns and the moment we reached the ship the Professor had been made prisoner.”

“Didn’t you see a struggle to pull down the flag when you looked through the glasses?” asked Tom.

“Yes, two or three men on the stern deck appeared to be battling with some others whom they finally drove off.”

“Then depend upon it, the whole crew has not mutinied. Probably the men you saw were the Professor and the Captain or some other officer who had remained loyal,” struck in Dick Donovan. “Come to think of it, I believe I saw a despatch in the paper some time ago about this very yacht,” he went on. “The cable came from the Canary Islands and said that the Valkyrie had put in there with a mutinous crew and shipped another one. She then proceeded on her voyage across the Atlantic. There was some mystery about her destination, but it was generally supposed that she had on board a party of treasure hunters bound to recover lost treasure somewhere in South America.”

“From what I’ve heard dad say about Professor Von Dinkelspeil,” said Jack, “I don’t think the professor is much of a chap for that sort of thing. Dad said that he was a famous naturalist.”

“Maybe he was going to combine natural history and treasure hunting in South America,” suggested Dick. “Anyhow, one thing is sure; for some reason this new crew has mutinied like the old one. They now have possession of the ship and we are their prisoners. The question is, what are they going to do with us?”

Dick’s clear way of putting it made them all look serious. It was plain enough that, after treating them in the manner that they had, the mutinous crew could not afford to chance setting them ashore. In that case their ultimate fate remained a mystery.

“What do you think about it?” asked Tom, turning to Dick. In some way he felt that this bright-eyed, alert lad was more likely to have the key to the situation than any of them. But Dick shook his head perplexedly.

“What they mean to do with us depends a heap on what they intend to do themselves,” he said dubiously. “It’s my idea that, right or wrong, the rascals now in control of this craft must have had some sort of idea that she was on a treasure hunt. In that case, I think it’s likely that they may have secured in some way information as to where the treasure is, and are going after it themselves.”

“Then I wonder what they will do with us?” insisted Tom.

“By the grinning gondoliers of Granada, you’ve got me stuck. Maroon us, maybe, on some island, or——”

“Hullo! We’re moving!” cried Jack suddenly.

A perceptible vibration and hum ran through the yacht’s frame as her engines began to revolve. There was a port-hole in the cabin in which the boys were confined and Jack thrust his head out. But he could see no signs of the Wondership. Instead, through the rain which was now falling fast on a sullen, heaving sea, he could perceive, dimly, the distant coast line slipping by.

It was at this juncture that an odd sound came on the wall of the cabin.

“Somebody’s tapping!” exclaimed Tom, the first to solve the mystery.

“Sure enough,” rejoined Dick; “maybe it is your father. They may have put him in next door.”

“Hark!” exclaimed Jack suddenly. “Listen to those taps. Don’t you notice something odd about them?”

They listened in silence for a few minutes. Above the throbbing of the screw and the rush of water along the moving vessel’s side they could catch the odd rhythm of the taps being delivered on the cabin wall.

“By the ticker-tapes of Tripoli,” cried Dick suddenly, “somebody’s telegraphing us!”

“Yes; it’s the Morse code!” almost shouted Jack, and leaning against the wooden wall of the cabin he energetically rapped out a reply.