"Some loose rock caving in," answered one of the men. "Come on, finish up. We've only got one more hole to fill, and by that time Nash will be ready to hoist us up."
"That wasn't falling rock!" declared Smith. "Boys, I believe someone is spying on us. I'm going to take a look."
Seizing one of the torches he started toward where Dick and his companions were hiding.
"Come on!" exclaimed the millionaire's son, pulling Tim and Frank by the arm. "We've got to get out of this!"
They turned and ran, their footsteps echoing on the rocky floor of the mine. They could hear Smith coming after them. His torch flashed around the turn in the gallery. He caught sight of them.
"Stop!" he cried. "Stop or I'll shoot!"