For a few moments the three chums remained staring at each other. The news of Frank's disappearance came as a shock to Bart and Ned, just as it had to Fenn. And Fenn's last words set the others to thinking.
"What do you mean?" asked Ned.
"I mean that Frank's not himself lately," Fenn went on. "You must have noticed it as well as I."
"You're right," came from Bart. "There is something very strange about Frank, and I can't understand it. The more we talk about it the worse it seems."
"Unless—" began Fenn.
"Unless what?"
"Boys, I hate to mention it," said Fenn, with a strange air, and he looked all around as though he feared someone would hear him, "but I'm afraid Frank's mind is affected!"
"Do you mean he's crazy?" asked Bart, suddenly.
"No; not exactly that. But I think he has some secret trouble, and that he has worried over it so much he isn't quite himself. Don't you remember how interested he was in the King of Paprica," went on Fenn, referring to the incidents told of in the first volume of this series. "He thought the man was crazy, and he said he had been reading up a lot about insanity. I thought then maybe he had had some trouble in his family, and that might account for his not wanting us to seek to solve the mystery of the curious men."
"Nonsense!" exclaimed Ned. "Frank crazy? Why, he's no more crazy than I am!"