Holding the sailboat to its course, the two Cubs kept watch of the idle motorboat. Though they were too far away to be certain the craft was Mr. Manheim’s, they thought it bore a marked resemblance to the craft operated by Wilson Jabowski.
Presently, as the boys watched, they saw someone aboard the motorboat lower and raise a red flag three times in succession.
“What’s the idea of that?” Dan demanded, all attention. “They’re signaling!”
“To someone on Skeleton Island,” Brad added quietly.
Dan turned his gaze toward the island beach. A man stood there, apparently focusing his attention upon the motorboat. In answer to the signal, he raised and lowered his arm three times.
“What goes?” Brad muttered.
For awhile, the Cubs witnessed nothing more of interest. The man on the beach vanished from their range of vision, while the motorboat remained in the clump of bushes.
“Guess there’s nothing more to see,” Dan remarked in disappointment.
“Yes, there is!” Brad corrected, bringing the sailboat closer into the wind. “Listen!”
The two boys distinctly could hear the putt-putt-putt of a gasoline engine. For a minute they could not localize the sound. Then, from the far shoulder of the island, they saw a flat gasoline-propelled raft scooting across the river.