Determined to test this last idea, Nat slipped a short distance into the tunnel and listened intently.
A few seconds satisfied him that their imaginations had played them no pranks. Voices, far off, but apparently coming nearer, could be distinctly heard. Nat turned faint and sick for an instant, and a glance at Joe’s face showed him that his companion, too, was badly shaken. Nat did not blame him. The knowledge that mysterious beings of some sort were within the tunnel and coming toward them—perhaps on their track—gave him a most uncomfortable thrill.
He glanced down from the ledge on which they stood. The cliff face was smooth, although some metal rings showed that a ladder must once have existed by which the lake might be reached. Above the mouth of the tunnel the precipice was sheer also.
They were fairly trapped. As they realized this each lad instinctively grasped his stone-axe tighter. Nat crouched behind a boulder and Joe squeezed in close beside him.
“Who do you think they are?” he quivered, “survivors of the Lost Race, or—or——”
“I don’t know,” rejoined Nat, with what composure he could summon, “but this I do know, that they are not likely to be friendly if they find us.”
“Then there is a chance——”
“Yes, a chance that they may not come as far as this, or may not see us. They may be crossing some intersecting passage from a higher level.”
But a few minutes later the voices grew louder. The perspiration broke out on Joe’s forehead. He gripped his axe more tightly, but the sense of the mystery surrounding the beings who were approaching made him catch his breath in agitation. He felt as if he were in some nightmare.
“Mind! Don’t make a hostile move unless they attack us first,” warned Nat in an impressive whisper.