He pointed toward the island, and the occupants of the homing hydroplane saw, slowly rising from it in the still air, four straight columns of blue smoke.
"Looks like a signal of some kind," suggested Jack after a scrutiny.
"It's coming from about the place where we grabbed the kid," added Bill, a note of apprehension in his voice.
"I wonder what it signifies?" demanded Jack, whose face began to bear a somewhat troubled look.
"I can tell you," said Sam shortly, turning round from the wheel.
"You can?"
"Yes."
"Well, hurry up, then—what does it mean?" Jack spoke sharply at Sam's deliberation.
"It means," said Sam slowly, as if he wanted every word to sink in, "that the Boy Scouts have picked up your trail."