This was a great disappointment to the young inventor.
He shouted loudly again and again. But the two men were evidently far beyond hearing.
Frank kept on for some while in the hope of striking the trail again.
But in this he failed.
And now he was confronted with a startling fact.
This was that he was himself lost. He had not the slightest idea as to the direction to take to carry him out of the cave.
He wandered on and on for what seemed an eternity.
In vain he tried passage after passage.
The cavern was a veritable labyrinth. The more earnestly he tried to find his way out the deeper he got into the tangle.
Finally horror and despair began to settle down upon the young inventor.