There was no time to be lost. It suddenly occurred to Tom that the floor of the vestibule might have a kind of trapdoor. He pulled aside one of the rugs that covered the stones; there was indeed a trapdoor, not secured in any way. Down he went on hands and knees. Releasing the button of the electric torch so that the room was in darkness, he lifted the door half an inch, and guessed from the absence of light that the vestibule below was unoccupied. He cautiously raised the covering still farther and listened. There was no sound. He set his foot on a ladder beneath, and, moving so slowly and gently as to make not so much as a rustle, he went down step by step, pausing once or twice to strain his ears. Still there was no sound. When he reached the floor he ventured to flash a light around him. He saw he was in a stone-flagged chamber of equal size with the vestibule above. In the middle of the floor was a circular stone slab with an iron ring on it, and a thick iron bolt was shut into a socket. There was one door to the room, and, hurrying to it, Tom found that it was fastened on the outside. So far all was well. He softly summoned Abdul to descend. Then, drawing back the bolt and lifting the slab, he discovered a large opening leading to a spiral stone stairway. Again he hesitated. What lay below? The disappointment of finding the guest-chamber empty, the prolongation of the search, were beginning to tell upon him. But, crushing down his nervous excitement, he extinguished his torch again, and groped his way round and round until he came once more to level ground. All was still as death. A flash of the torch showed him that he was in a large vaulted corridor, paved with brick. Somewhere in this, he doubted not, was the door into the dungeons. In order to secure his line of retreat in case of emergency, he felt it was absolutely necessary first to secure the other entrance, wherever it might be, that was ordinarily used by the jailer. He soon discovered it by the aid of his torch. Here, as he feared, the bolts were on the outside, and the door was securely fastened. Was it possible to barricade the door from the inside? The whole place was empty with the exception of a number of manacles and like effects, and a long hammer, which Abdul said, in a whisper, was used by the Moorish jailers in fastening the chains round their victims’ ankles. But there was nothing that promised to be of service as a barricade. At any moment the jailer, if he had not taken panic from the discharge of the sentry’s musket, might enter to assure himself of the security of his prisoners. Could anything be done to delay him? For Tom felt that it was not only a question of the jailer, but of others who would no doubt hasten to his assistance.