was apparently untenanted by living beings. The mummy of Ptahmes still lay upon the couch. The straps which had fastened Belleville to the chair were all unfastened and Belleville himself had disappeared. Yet there were noises in the room, noises of footfalls and the tinkling of glass. Presently I saw a large glass phial move quietly from a marble slab and stand poised in air. A second later the stopper, which had been laid beside it, sprang up, too, and settled neatly in the phial's mouth. Then the bottle leaped up high into the air and settled, with mysterious precision, on a shelf. I stared at these wonders half-understanding, half-dazed. But soon I comprehended all. Belleville's voice speaking in Arabic came to me through the hush. "That will do, I think. There only remains for us to steal upon him now and take him by surprise. Serve me well in this, Ptahmes, and I shall treble your reward." "The man is of iron strength, master," answered the Arab's voice. "It is true that we are two to one and he is unsuspicious, but I should like well to have a knife." "Nonsense," retorted Belleville. "I cannot make steel invisible. We must needs trust to the sandbags. Now lead on to the lady's room and take care from this moment that you make no sound." On this I left the doorway and, slipping into the opposite corner, pressed flat against the wall. Presently the door creaked open and I heard the noise of breathing. I followed it as gently as a shadow, halting sharply when I could not hear it or it grew too near. I was weaponless--for I had left Belleville's revolver in the laboratory ere for the first time leaving it. But still, I dared not arm myself, for to have done so would have given my adversaries, sooner or later, a certain clue to my position; and my only hope of worsting them now consisted in preserving my absolute invisibility and at the same time knowing where, in the general sense, they were. My first great difficulty arose in the passage of the outer door. I dared not slip out with them, and since they locked it after them, I was forced to wait some time before I deemed it safe to open it again. Thus, when I reached the outer passage there was absolutely nothing left to guide my steps. However, I hurried to the arch and thence looked forth along the bifurcated corridor. Seeing and hearing nothing, I sank to the floor, and like an Indian pressed my ear against the boards. One far-off panel a little later creaked distinctly. Wood, though carpeted, is a fine sound conductor. This gave me the direction. Hot foot I followed it. But soon I came to a corner and beyond a short, wide cul-de-sac, with three closed doors. Here I stopped with straining ears and listened with a beating heart and bated breath. The conspirators were there, beyond the scope of doubt; and presently I knew the door they wished to pass. I saw the handle turn and heard a sigh. "Locked," murmured a voice in English--then in Arabic it breathed. "Keep closely