But Professor Bumper proved to be above suspicion. Carefully guarded inquiries made of the captain, the purser and other ships' officers, brought out the fact that he was well known to all of them, having traveled on the line before.
"He is making a search for something, but he won't say what it is," the captain said. "At first we thought it was gold or jewels, for he goes away off into the Andes Mountains, where both gold and jewels have been found. He never looks for treasure, though, for though some of his party have made rather rich discoveries, he takes no interest in them."
"What is he after then?" asked Mr. Titus.
"No one knows, and he won't tell. But whatever it is he has never found it yet. Always, when he comes back, unsuccessful, from a trip to the interior and goes back North with us, he will remark that he has not the right directions. That he must seek again.
"Back he comes next season, as full of hope as before, but only to be disappointed. Each time he goes to a new place in the mountains where he digs and delves, so members of the parties he hires tell me, but with no success. He carries with him something in a small iron box, and, whatever this is, he consults it from time to time. It may be directions for finding whatever he is after. But there seems to be something wrong."
"This is quite a mystery," remarked Tom.
"It certainly is. But Professor Bumper is a fine man. I have known him for years."
"This seems to dispose of the theory that he planted the bomb, and that he is one of the plotters in the pay of Blakeson & Grinder," said Mr. Titus, when he and Tom were alone.
"Yes, I guess it does. But who can have done it?"
That was a question neither could answer.