In the silence which followed, a faint, regular, scraping sound came from their right. It was so slight that for a minute or two neither of them could place it. At length they decided that it came from around the corner of the building, a spot which they could not see from their present position at the entrance of the plateau.
Scrape, scrape, scrape. Scratch, scratch, scratch. It sounded, with the regularity of clockwork.
Buckhart eyed his chum with a puzzled expression on his face.
“What the deuce is it?” he whispered.
“I’m not sure,” Dick returned, “but it sounds like filing—as though somebody was filing an iron bar. I’m going to find out.”
He dropped down on his hands and knees and commenced to creep slowly through the scattered boulders to the right. Brad promptly followed him, and in less than five minutes they were ensconced behind a great rock, from which a very good view of that side of the house could be obtained.
There was a momentary pause, and then they both peered cautiously around the corner of the boulder.
The next moment the Texan caught his breath with a sudden, swift intake, his eyes widened with astonishment. Dick, crouching beside him, pressed his chum’s arm warningly, without for an instant averting his own gaze from the surprising sight before them.