"A little suspicious, eh?" said Warrender. "Stamp on the stone."
"Hold hard! What if that fellow is underneath it?"
"We've got to the point where we must take risks. But it's not credible that any one actually lives down below, even if there is a below. Try a kick or two."
But there was no ringing sound when Armstrong stamped; the stone was either laid firmly on the earth, or it was so thick that, if there was a hollow beneath it, the fact would not be detected. Nor, when Armstrong trod heavily all over its surface, was there the slightest sign of movement.
"Feel along the edge," Warrender suggested.
Armstrong went down on hands and knees and drew his finger along the base of the lowest step.
"A slight crack here, at the left end," he said.
"Big enough to get your finger in?"
"No; it can't be more than an eighth of an inch wide. It's upright, between the step and the wall. Looks as if the stone has shifted."
"Well, if you can't get your finger in, try your knife blade."