As the Sleuth plunged through the water, in the very shadow of the ship, Joe suddenly gave an exclamation of surprise.
"Frank! Look up on deck—quick!"
Frank glanced hurriedly upward. He was just in time to see the figure of a boy moving away from the rail, but there was something familiar about the young fellow that made him look incredulously at his brother.
"Chet!"
"I'm sure it's him," returned Joe hurriedly. "I didn't get a very good look at his face, because he only looked over the rail and then he drew back—but I'm almost positive it was Chet!"
"But what on earth can he be doing on that schooner?"
"Probably he's a prisoner. Let's give him a hail."
They shouted the name of their chum half a dozen times, but their only response was from a villainous looking sailor who glared over the side at them and bade them get away from the ship.
"No use causing trouble," said Frank, in a low voice. "We'll go now, but we'll come back later."
He steered the motorboat away from the vicinity of the schooner, but instead of going on into the harbor he put out to sea again.
