"Look here," he said. The joint between the flagstone and the brickwork of the floor had a sharp, well-defined edge. The crevice was free from coal dust.
"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.
"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."
"Wait a bit, there’s another crack, smaller still, right along the edge of the step, between it and the upright slab."
They had both lowered their voices to a whisper. Armstrong gave the upright a push, near the middle. It was firm, unyielding. But pushing leftwards, he felt a slight movement, and at the extreme end, a very gentle pressure caused the slab to swing inwards easily, the right half of it at the same time moving outwards.
"By gum, it works on a pivot!" exclaimed Armstrong, under his breath. "We’re on the track! But this opening’s only about six inches wide; nobody but a baby could crawl through it."
For a few moments they held their breath, listening for sounds. All was silent. Then Warrender dropped on all fours and shone his torch into the dark gap. The space was empty. Armstrong thrust in his hand, and felt over the earthen floor, then along the edge of the flagstone, and finally beneath it.
"There’s a hollow space here," he said. "And, I say, here’s a metal hand-grip just below the flagstone."
He tugged it; there was no movement. He pushed it on each side in turn, still without result. Baffled, he sat on his haunches.