Joe could hear his brother scrambling along through the little corridor in the rocks. After a while the sounds died away. It was dark and lonely in the cavern in which he stood. He waited for Frank's summons to follow.
After five minutes there was still not a sound from the opening into which his brother had disappeared. Joe began to get anxious. He knelt down and flashed his light into the interior of the passage. There was no sign of Frank.
"I wonder if anything has happened to him," he muttered.
When another five minutes passed and there was still no sign of his brother, Joe decided to invade the passage himself. Anything might have happened. Frank might have been overcome by poisonous gases in the depth of the mine. He might have tumbled down some unseen pit and hurt himself. Flashing the light ahead of him, Joe crawled into the narrow corridor in the face of the rock.
For several yards the passage extended directly ahead; then there was a turning. Examining the corridor, Joe saw that it was not a natural opening in the rock, but had been constructed by human hands, for the marks of pick and shovel were plainly visible. It had been blasted out of the rock, and for a short distance the dimensions of the passage were of good size, but gradually they narrowed.
He had just gone past the turn in the tunnel when he heard a faint shout.
"Joe! Joe!"
It seemed to come from a long distance, and there was a note of appeal in it that told the boy his brother was in danger.
Scrambling on through the tunnel that seemed to open before him in the vivid circle of light, he made his way toward Frank. He heard the cry again, and this time it was louder. He shouted back:
"I'm coming. What's the matter?"