They advanced several paces. The rustling sounds became multiplied. Then, suddenly, Frank caught sight of two gleaming pinpoints of light glowing from the blackness.
"What's that light?" asked Joe.
"I don't know. I'm going closer."
Frank stepped forward again. As he did so, instead of two pinpoints of light, he saw two more, then two more, until at least a dozen of those strange glowing green spots shone from the darkness, reflected in the glow from the flashlight.
"Animals," he said quietly to Joe.
At the same instant he heard a low, menacing snarl.
The glowing greenish lights began to move rapidly to and fro. Into the radiance of the flashlight shot a lean, grey form that disappeared as swiftly as it came.
A prolonged and wicked snarling rose from the gloom. Frank glanced to one side and saw that two of the greenish lights had moved until they were circling behind him. He leaped back.
"We'd better get out of here!" he said. "Those are wolves."
But when the boys turned to retrace their steps they were confronted by a lean form that barred their way to the cave entrance, and in the glow of the flashlight they saw two greenish eyes that glowed fiendishly and two rows of sharp white teeth bared in defiance.