At the end of the corridor was another door. Fall fitted a key and swung open the heavy iron portal and the two men passed through to a darkened chamber. Fall found the switch and illuminated the apartment. It was a little room innocent of windows, and lit as all the rest of the basement was by cornice lamps. In one corner was a grey-painted iron door. This Fall pushed aside on its noiseless runners. There was another elevator here. The two men stepped in and the lift sunk and sunk until it seemed as though it would never come to the end. It stopped at last, and the men stepped out into a rock-hewn gallery. It was easy to see that this was one of the old disused galleries of the old mine over which the house was built. Fall found the switch he sought and instantly the corridor was flooded with bright light. On a set of rails which ran the whole length of the gallery to a point which was out of sight from where they stood, was a small trolley. It was unlike the average trolley in that it was obviously electrically driven. A third rail supplied the energy, and the controlling levers were at the driver's hand. Farrington climbed to the seat, and his companion followed, and with a whirr of wheels and a splutter of sparks where the motor brush caught the rail, the little trolley drove forward at full speed. They slowed at the gentle curves, increased speed again when any uninterrupted length of gallery gave them encouragement, and after five minutes' travel Farrington pulled back the lever and applied the brake. They stepped out into a huge chamber similar to that which they had just left. There was the inevitable lift set, as it seemed, in the heart of the rock, though in reality it was a bricked space. The two men entered and the lift rose noiselessly. "We will go up slowly," whispered Fall in the other's ear; "it will not do to make a noise or to arouse any suspicions; we must not forget that we have T. B. Smith to deal with." Farrington nodded, and presently the lift stopped of its own accord. They made no attempt to open whatever door was before them. They could hear voices: one was T. B.'s, and the other was unmistakably Poltavo's, and Poltavo was speaking. Poltavo was offering in his eager way to betray the men who sat in the darkness listening to his treachery. They heard the motor-car's arrival outside, and presently T. B.'s voice announcing his temporary retirement. They heard the slam of the door, and the key click in the lock, and then Dr. Fall stepped forward, pressed a spring in the rough woodwork in front of him and one of the panels of the room slid silently back. Poltavo did not see his visitors until they stood over him, then he read in those hateful faces which were turned toward him an unmistakable forecast of his doom. "What do you want?" he almost whispered. "Do not raise your voice," said Farrington in the same tone, "or you are a dead man." He held the point of a knife at the other's throat.