Gurdon could hear the sound of labored breathing as if the unseen man was struggling with some heavy burden. Presently some square object was deposited on the floor of the lift. It seemed to slip from someone's hands, and dropped with a heavy thud that caused the lift to vibrate like a thing of life." "Clumsy fool," a voice muttered. "You might have dropped that on my foot. What did you want to let go for?" "I couldn't help it," another voice grumbled. "I didn't know it was half so heavy. Besides, the rope broke." "Oh, are you going to be there all night?"--another voice, with a suggestion of a foreign accent in it, asked impatiently. "Don't forget you have to bring the man down yet, and see that the boy is taken to his place. Now, up with it." Standing there, holding on to the rope and quivering with excitement, Gurdon wondered what was going to happen next. Once more he felt himself rising, and an instant later he was in the light again. He waited till the lift had reached his own floor; then he jumped quickly down, taking care as he went to note the heavy box which lay on the floor of the lift. A corner of it had been split open by the heavy jar, and some shining material like sand lay in a little heap, glittering in the rays of the electric light. Gurdon stood there panting for a moment, and rather at a loss to know what to do next. Once more the lift came down, this time with two boxes of a smaller size. They vanished; and as the lift rose once again, Gurdon had barely time to hide himself behind the bedroom door, and thus escape the observation of two men who now occupied the cage. He just caught a fleeting glimpse of them, and saw that one was an absolute stranger, but he felt his heart beating slightly faster as he recognised in the other the now familiar form of Mark Fenwick. The mystery was beginning to unfold itself. "That was a close thing," Gurdon muttered, as he wiped his hot face. "I think I had better go back to my own room, and wait developments. One can't be too careful." The lift-boy was still sleeping on the bed; but his features were twitching, as if already the drug was beginning to lose its effect. At least, so Gurdon shrewdly thought, and subsequent events proved that he was not far wrong. He was standing in his own room now, waiting by the ventilator, when he heard the sound of footsteps on the other side of the wall. Two men had entered the room, and by taking a little risk, Gurdon could see that they were examining the unconscious boy coolly and critically. "I should think about five minutes more would do it," one of them said. "Better carry him out, and shove him in that little sentry box of his. When he comes to himself again he won't know but what he has fallen asleep; barring a headache, the little beggar won't be any the worse for the adventure." "Have we got all the stuff up now?" the other man asked.