"He'll understand that if he's up on Boy Scout literature," suggested
Sandy. "He ought to be wise to the signs of the different patrols if
he's a good Boy Scout."

There was a short silence, broken only by the constant drip of the
water in an adjoining chamber and then the call of the pack came
again, clearly, sharply and apparently only a short distance away.

"What did Mr. Canfield call those two boys we are looking after?"
asked Sandy, after waiting a short time for the repetition of the
sound.

"Jimmie Maynard and Dick Thompson," replied Tommy.

Sandy threw out his chest and cried out at the top of his lungs.

"Hello, Jimmie! Hello, Dick!"

The lad's voice echoed dismally throughout the labyrinth of passages,
but there was no other reply. Tommy and Sandy gave the call of the
Beaver Patrol repeatedly, but the call of the Wolf pack was heard no
more.

"I'll bet it's some trick!" exclaimed Sandy after waiting in the
chamber for a long time in the hope of hearing another call from the
boys who were hidden somewhere behind the cribbing.

"What do you mean by trick?" demanded Tommy.