As soon as he was free he made a tour around his dungeon, rather by way of distraction and to stretch his legs than with any idea of making a discovery that would further his escape.
The vault was pitch dark. He had seen it by the light of the oil-lamp during the visits of Minghal and the khansaman, but taken no particular note of it. He now went round it, feeling the walls with his hands. They were of rough-hewn stones; there was no variation except at the door. He shook that: it was locked fast. He went back to the staple and sat down; after a time, having nothing better to do, he started again, and examined the door by touch more carefully. There was no handle, not even a keyhole on the inside. Thinking he heard footsteps, he retreated so hastily that he narrowly escaped overturning the pitcher of water. It was a false alarm. Once more he went round the walls, this time in the opposite direction.
And now, as he drew his hand along the wall, he fancied that one of the slabs of stone protruded a little further into the room than the others. All the stones were rough and ill-fitting, but this protuberance awoke his curiosity. Had he detected a slight movement as he first pressed it? He pushed hard at it--upwards, downwards, sideways, but without result. Surely he had been mistaken. He would try again. This time he pushed gently, and thrilled all through when he felt an indubitable movement, though very slight. Now, instead of pushing, he pulled outward. The stone yielded. He pulled harder; it moved reluctantly, but it did move, and by and by he was able to get his fingers round the edge of the slab. Another pull, and it came a few inches from the wall, then stopped.
He was puzzled. He pushed at the stonework immediately around the slab. There was no result. He tried a few feet to the right--in vain; then to the left. Something seemed to give slightly. A harder push, and the slab moved inward, slowly revolving on a vertical axis until it stood perpendicular to the surface of the wall.
With beating heart he crawled through the opening, and found himself in a stone passage, so low that he had to stoop, so narrow that there was not an inch to spare on either side. In a dozen paces he reached the end--a dead stone wall. There must be an outlet, but where? He felt over the wall and discovered a protuberance similar to that in the room he had left. He pushed and pulled in the same way; the slab moved; a light shone through the crack between it and the wall. He peeped through. There was Craddock Sahib reading at his little table by the light of a lamp.