When they came to the place where the tunnel had seemed to end, they surveyed it dubiously.
"I'll go ahead," said Frank. "Like as not, I'll get stuck in here and you'll have to come in and pull me out."
He wedged himself into the opening between the rocks, holding the flashlight before him.
To his surprise he found that although there was a blank wall immediately ahead, the tunnel turned sharply to one side and in the glow of the light he saw that it continued for some little distance, a very narrow passage, but one that offered sufficient space for him to continue.
"It doesn't end here after all," he called back to Joe. "Perhaps it does lead outside."
He went on. Joe scrambled through the opening and followed close behind.
With growing elation Frank found that the tunnel continued. When he had gone about fifteen yards he rounded a sharp corner, and gave a cry of delight.
Here, on the wet floor, he spied the imprint of a man's shoe!
"There's been some one here before us," he said to Joe, in excitement. "A footprint!"
"Which way does it lead?"