"That's what makes the whole affair the more mystifying," rejoined Rob. "What can have become of him?"
"Well, if he's on the island, we'll find him," he continued; "and if he isn't—"
"We'll find him anyway," declared Merritt in a determined voice.
"That's the stuff!" warmly exclaimed the other. "And now I'm going to take a cruise round to the other side of the island, and see if I can find out anything there."
A few seconds later he was in the dinghy and sculling out over the water to the speedy Flying Fish. In a short time he was off.
As the "chug chug" of the motor grew fainter, Merritt turned to young Thompson.
"Don't breathe a word of this to the others till we know for certain that Digby has vanished," he said.
The other boy nodded.
"I understand," he said, and the look with which he accompanied the words rendered Merritt perfectly confident that he would be obeyed.
"And now let's rouse out Andy Bowles and get him busy with that tin horn of his," cheerfully went on Merritt, walking toward Andy's tent.