“Oo! oo!” gasped poor Indian. “Don’t talk that way, please. Bless my soul, I know I shall drop dead with fright.”
At that same instant something happened so unexpected and so horrible that it struck them motionless and chill.
A deep low groan, as if of agony, echoed through the lonely cave!
For a moment the Seven glanced at each other in consternation and dread. They were almost paralyzed by the sound, which had evidently come from one of the inner recesses of the cavern. Poor Indian had sunk down on the ground in a heap.
“What’s that?” they cried, and then listened.
But the groan was not repeated. They waited in fear and trembling, but the rocks gave not another sound, and suddenly Mark sprang to his feet.
“Fellows,” he cried, “there’s somebody in here! Who’ll follow me?”
The faithful Texas sprang to his side, and the rest followed, though trembling and quaking in every joint.
Mark was as much terrified as any of them, but he shook it off with a powerful effort and gazed resolutely about him.
“There’s no use having any nonsense about this!” he exclaimed. “None of us believes in ghosts, so what’s the use of being scared. There’s only one thing possible, there’s somebody in here.”