"Why should it have been left so?"

"Because the treasure they expected had never arrived. It is possible that when the Incas discovered the treasure in that chamber we searched, they may also have found this entrance. It may have been shown to them by one of the prisoners, and they may have broken the stone here into pieces as they broke that over the chamber afterwards. Seeing what a splendid hiding-place it was, they may have, when the Spaniards first arrived, made another stone to fit, with the intention of using it for a hiding-place themselves. The fact that the stone was left so that it could be at once opened is conclusive proof to my mind that the treasure never came. That heap of sand, small stones, and chips of rock is another proof that they were ready to receive treasure, and it was probably swept out of the chamber that is behind here, and would, of course, have been removed when the treasure was put in and the door closed; but as the treasure never did come, it was left where it lay. However, we will now go and see. I have only kept you waiting because I did not want you to be disappointed."

One by one they crept through the opening. For four feet in, the passage was the same width as the stone, but two feet deeper; then it at once opened into a large cavern.

"This wall was four feet thick, you see, Dias. Apparently squared stone was only used for the facing, as the stones are of irregular shape on the back. This would be a natural cavern, and a splendid hiding-place it makes. No doubt its existence was one of the reasons for building this castle."

The cavern was some twelve feet wide and thirty feet high at the mouth; the floor sloped up sharply, and the sides contracted, and met forty feet from the mouth. The floor had been cut into steps two feet wide, running across the cave and extending to the back. These steps were faced with a perfectly flat slab of stone. The cave was empty.

The natives uttered loud exclamations of disappointment and regret.

Harry had so thoroughly made up his mind that nothing would be found there that he surveyed the place calmly and in silence. Bertie imitated his example with some difficulty, for he too was bitterly disappointed.

"You see, Dias," Harry went on quietly, "this place was prepared to receive treasure. The steps have all been swept perfectly clean. You see, the gold could be piled up, and no doubt the steps were cut and faced with stone to prevent any gold-dust that might fall from the bags, in which, no doubt, it would be brought, and small nuggets, from falling into the cracks and crevices of the rock. I should say that in all probability they expected that treasure ship that was lost, and had everything in readiness for hiding the cargo here directly it came. It never did come. The door was shut as far as it could be without the bolt falling down and fastening it; then they waited for the ship; and if it did not arrive, other treasure might be brought by land. Well, it cannot be helped. So far we have failed. There may still be treasure hidden somewhere. We cannot say that we have searched the place thoroughly yet."

For another six weeks they worked hard. The wall was broken through in several places, but no signs of the existence of any other cavern or hiding-place was discovered.

"I should give it up," Harry said, when at the end of that time they were sitting gloomily round the fire, "but for one thing: I can see no possible explanation why a party of men should have been left here, and a guard kept, for perhaps a hundred years, perhaps more, and the stories about demons been circulated, and people who ventured to approach been murdered, unless there had been some good reason for it. That reason could only have been, as far as I can see, that there was a treasure hidden here. I have turned it over and over in my mind a thousand times, and I can think of no other reason. Can you, Bertie, or you, Dias?"