"I'm sure I can't tell you," replied Mr. Perry. "But you have a dandy
field to work on. All you need is a little imagination; then begin to do
a little head-work, and before you know it you'll have a lead to work on.
And let me add something more. There are two things in this world, which,
working together, can knock a mystery into a cocked hat more successfully
than anything else in the world that I know of."

"I bet I know what they are," Cub volunteered, eagerly.

"Mathematics and imagination," almost shouted Hal in a wild scramble of
mind to beat Cub with the answer.

The latter cast a wrathful glance at the saucy youth who had broken in
ahead of him.

"Tee-hee!" laughed Bud with fitting imitation of Hal's characteristic
vocal merriment.

As for Tee-hee, that worthy individual preserved his dignity for
the nonce.

"Well," laughed Mr. Perry; "You've hit the nail on the head, but I
venture to say you can't explain why mathematics and imagination can put
a mystery to rout."

Hal confessed he was unable to explain.

"It's too much highbrow for me," he said. "And I bet it's too much
highbrow for Cub."