Then he stole out, groped his way to the wall, and passed his hand along the outer side until he came to the nail.

He found it.

It had been made secure, and from it depended a thin string.
He set to work at once to draw up the string.

There was a small weight attached to it, which rose slowly until it reached his hand.

It was a stone about as large as the fist, and of a whitish colour..