“what had we better do to him?” asked andy, as they neared the prostrate man.

“tie him up so he can’t get away again,” replied frank, as he glanced at the seaman who was rapidly rowing away. “if we keep him, now that we’ve got him, he may tell us what we want to know. and we’ve got the wreck of the motor boat, too. we sure ought to get at the bottom of this mystery now.”

“well, we deserve something after all we went through,” remarked the younger lad, as he thought of the rising tide in the cave.

“that fellow is in a hurry all right,” went on frank, with a wave of his hand toward the sailor who was now some distance out. “i guess he hit him a pretty hard blow.”

“maybe he killed that man, and is afraid we’ll arrest him,” suggested andy.

“nonsense! i don’t believe that man is dead.”

they were close to him now and stopped to observe the quiet figure. they hesitated for a moment, for, though they had made up their minds to make the man a prisoner, it was the first time they had done anything of the sort, and, naturally, they were a little timid.

suddenly the figure on the sands stirred, and there came a murmur from the mysterious man.

“if we’re going to do anything, we’d better get at it,” suggested andy. “he’ll come to his senses in a minute and we’ll have our hands full. he’s a powerful fellow.”

“that’s so. i wonder where there’s some rope?” asked frank.

andy motioned to the wreck of the motor boat, near which the man lay.

“there’s plenty,” he said. “they had a long rope to tow it with. i’ll get some.”

holding the cord in readiness, the two brothers approached the man, one on either side.

“you take his feet, and i’ll attend to his hands,” whispered frank. “have a slip-noose ready to put on, and pull it tight. then take several turns and we’ll truss him up.”

they worked silently and rapidly. andy slipped the coil of rope about the man’s ankles, and pulled the noose taut. as he was doing this the man stirred and murmured:

“i’ll get even with you for this, hank splane!”

“quick! he’ll come to in a minute!” whispered andy.

“i’ve got him,” answered frank. as one of the man’s arms was partly under him the lad had to pull it out before he could slip the noose around it. but he finally accomplished this, and, just as he had it tight, the fellow suddenly sat up.

“here! what’s this? splane, are you crazy to tie me up this way? let me go, i say, or i’ll make you sorry for this. let me go, i say!”

he was struggling violently, swaying to and fro as he sat on the sands. then his vision, which was probably obscured by the blow he had received, cleared, and he saw the two boys holding the ends of the ropes that bound him.

“oh, it’s you; is it?” he gasped, plainly astonished. “didn’t i tell you to stop following me? i won’t have it! if you don’t—” he stopped short. a look of wonder followed by one of alarm came over his face.

“the cave!” he exclaimed. “i left you in the cave. the tide was rising. you—you—”

“yes, we escaped, but no thanks to you!” exclaimed frank sternly. “you meant us to be drowned, but we found a way out, and now we have you just where we want you, you rascal! you’ll tell us what we want to know, you’ll clear up the mystery of paul gale, and you’ll confess what you want of this motor boat now, i guess.”

“suppose i refuse?”

“then we’ll take you before the authorities.”

“ha! ha! a likely story. marooned on this lonely island you can’t do much. you see i happen to know your boat is gone, and—”

“gone, yes, because you took her,” interrupted andy.

“no, i didn’t take either your sailboat or the rowboat,” spoke the man simply. “i wanted to, but some one else got ahead of me. i had to row away from the island as the storm came up, and it was no joke, either.”

“then who did take our boats?” asked andy blankly.

“i don’t know,” replied the man. “but i do know that you have more than you bargain for if you think you can make me talk. there is no one on this island but ourselves, now that splane played me a mean trick, and deserted. talk of authorities! ha! ha! it’s a joke,” and he pretended to be amused.

“we’ll soon be off the island,” said frank, with more confidence than he felt. “our father will be looking for us, and may arrive at any minute.”

the man uttered an exclamation beneath his breath. evidently he had not counted on this. the two boys stood regarding him. now that they had him, they hardly knew what to do with the fellow.

with a suddenness that was surprising, considering that his feet were tied, the man managed to stand upright. then, with a mighty effort, he tried to loosen the rope around his hands.

“when i get loose i’ll show you what it means to trifle with me!” he shouted. “you’ll be sorry you ever meddled in this matter! wait until i get this rope off!”

he tried desperately to get it off his hands, and andy saw the strands loosening.

“quick, frank!” cried the younger lad. “we’ve got to take some more turns on that! i’ll help! he can’t hurt us now!”

the two brothers fairly threw themselves on their prisoner and all three went down in a heap on the sands.