"Well, there's not very much, I'm afraid, Rob," began Andy, "but we found something that may give us a clue. About half a mile down the beach there's the distinct mark of a boat keel where it was drawn up on the hard sand and the marks of three separate pairs of feet."
"Good," exclaimed Rob, "that's something and half confirms my suspicion. Go on, Andy, what else?"
"Well, we examined the marks carefully and found that two pairs of feet wore good shoes and the third a very broken, disreputable pair."
"Yes," exclaimed Rob, while the others listened breathlessly.
"Of course that indicated to us that three persons must have carried Joe off—for I don't think there's much doubt now that he was carried off, do you?"
"I don't," said Rob sadly, "but for what possible motive?"
"I have it," suddenly exclaimed Tubby Hopkins, snapping his fingers, "you remember the day of the aeroplane model contest?"
"Yes, but what—" began Rob.
"Has that to do with it," finished Tubby for him. "Everything. It was Joe who first told the committee that Jack's model was a bought one and so lost him the fifty-dollar prize."
"By cracky, that's right!" assented Rob, "and you think that Jack and his gang have carried him off in revenge for it?"