“I won’t forget it,” the man grinned. “Good luck to you.”
Before turning back to the shack he first examined his captive’s hands and made sure that he had not loosened the cord.
“You’ve got them tied pretty tight,” the man remarked.
“I intended to,” Bob returned grimly. “But you won’t suffer any if you don’t try to get away.”
“I tried that while you were gone before.”
Back again inside the dark cave he began a systematic examination of its walls. That there was a secret passage way he felt sure. As he had said a man doesn’t pass through solid rock and the man he had tied outside had, in some way, made his escape, therefore there must be a way.
Foot by foot he made the circuit of the room, throwing the rays of his flash light on every inch of the wall. He had covered three sides when a faint sound caught his ear. At first he feared that he had been mistaken, but a moment later it was repeated a trifle louder. It sounded as though some one was striking one rock against another, but it seemed a great way off and he was unable to determine the direction from which it came.
“Jack.” He shouted the name as loudly as he could.
Now the taps came at closer intervals and in a moment he realized that there was a meaning to them.
“B-O-B.”