Without further ado, however, we seized pick and spade, and commenced to open the ground at the spot where it sounded hollow. At a depth of about two and a half feet, through stone and rubbish, we came upon a big flat slab, like a paving-stone.
Was it possible that the historic emeralds of Lucrezia Borgia were actually hidden beneath? Our excitement knew no bounds, especially so as Selby had loosened his gag, and we could hear him shouting and cursing in the distance. We had, however, no fear of his shouts attracting attention, for the spot was far too lonely, and his voice would not reach the river bank, so broad was the stream.
With a keen will we all worked, digging out the earth from around the slab until at last I drove the end of a pick beneath it, and, using it as a lever, succeeded in raising the huge flat stone sufficiently to allow the insertion of a crowbar. Then, all bending together, we raised it up, disclosing a deep, dark, cavernous hole which emitted the damp, earthy smell of the grave.
“Who’ll go down with me?” asked Fred.
“I’ll go presently,” volunteered Sammy, “when the place has had a bit of airing. There’s foul air there, I expect. Perhaps it’s a well.”
Fortunately we had provided ourselves with two hurricane lanterns, and one of these I lit and lowered into the hole by a string. It remained alight, showing us, first, that the air was not foul; and, secondly, that the place was not a well, but a small stone chamber, the floor of which was covered with broken rubbish, and that the walls were black with damp and slime—not at all an inviting place in which to descend.
Fred was the first to let himself down, and, taking the lantern, he disappeared.
“I say,” he cried a minute later, “it isn’t a chamber. It’s a kind of low tunnel—a subterranean passage!”
The announcement caused us even increased excitement; and, while Sammy and I let ourselves down to join Fred, we arranged that Walter, armed with Selby’s revolver, should remain on the surface and so guard against any trickery on the part of the man who was our prisoner. It would, we knew, be easy enough to trap us like rats while we were down there.
“Wait till we come back, Walter!” I cried, and then, with my lamp, followed my two companions into the narrow burrow which ran down a steep incline in a southerly direction. Fred went first; but so dark was the way and so blocked in parts by fallen stones that our progress was very slow. We remembered that in such places of secret communication there were often pitfalls for the unwary; hence the caution we exercised.