Sime nodded.
"You are right. What does that mean?"
Dr. Cairn directed the ray of light down behind a little mound of rubbish into a corner of the wall.
"It means," he said, with a subdued expression of excitement, "that we have got to crawl in there!"
Sime stifled an exclamation.
One of the blocks of the bottom tier was missing, a fact which he had not detected before by reason of the presence of the mound of rubbish before the opening.
"Silence again!" whispered Dr. Cairn.
He lay down flat, and, without hesitation, crept into the gap. As his feet disappeared, Sime followed. Here it was possible to crawl upon hands and knees. The passage was formed of square stone blocks. It was but three yards or so in length; then it suddenly turned upward at a tremendous angle of about one in four. Square foot-holds were cut in the lower face. The smell of incense was almost unbearable.
Dr. Cairn bent to Sime's ear.
"Not a word, now," he said. "No light—pistol ready!"