much risk of capture. They'd hardly go to the trouble of outlining all that if they didn't mean something by it."
"Yes, if the letter was only sent as a blind to bring dad back to Bayport you'd hardly think they'd go into all that detail."
"Still," Frank pointed out, "here we are, safe and sound. Haven't been kidnapped yet, and nobody has tried to kidnap us. If that letter had been sent to Chet's people, for instance, or to the Hoopers, they would have something to worry about." Suddenly he stopped and looked at Joe. "Say!" he exclaimed. "There's an idea!"
"What?"
"Chet and Biff!" declared Frank excitedly. "Don't you see? This may have something to do with them. Chet and Biff are missing. Perhaps they have been kidnapped."
"But why should any one kidnap them?" Joe looked wonderingly at his brother.
"In mistake for us. Don't you see it? Perhaps this gang mistook Chet and Biff for you and me and kidnapped them! Then they wrote the letter to dad."
"Gee, I never thought of that!" Joe exclaimed. "I'll bet dollars to doughnuts that you're right."
"Don't you remember the day we were all out in the boat and the three men came so close
