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 fol