"A most hospitable door," Carl said. "Yes, a door without a latch-key," Pierre replied. "Then how do you open it?" His question was answered with the silent movement of the steel door, as if someone had opened it from the inside; although in the dim light of the reception hall, Carl could see no sign of another occupant. "It opens by cutting off the beam of light that passes from the post at one side of the door to the post on the other," Pierre said, as he ushered Carl into the hallway. Carl turned and watched the door close silently behind him. "You have them in some of your modern office buildings," Pierre continued. "This door has opened that way for the past forty years. My father developed the principle. Come, we will go to my observatory." Pierre led Carl to a narrow stairway leading upward to the north wing. Up one flight they moved silently. A dim blue light illuminated the landing, and shed its ghostly rays down another hall. Up another flight, leading in the same general direction, they walked. Carl felt as if he were climbing slowly through a mad dream. Passing through a heavy, rivet-studded door, they entered the laboratory. The room was vast, covering the entire top floor of the house. The glass enclosure which he had seen from outside served only one end and corner of this amazing room. The walls were of a peculiar gray, glowing softly as if phosphorescent. Throughout the entire expanse of the room there was arranged an incalculable assortment of instruments, switch-boards, control-panels, glass and polished chromium, copper and brass. To Carl it was like suddenly entering a room fitted with all the strange instruments of the alchemists, and yet it was like looking ahead, fifty, a hundred or even two hundred years into the future. Pierre led the astounded Carl over beneath the glass dome. Here seemed to be the major control position for all the complex horde of machines that filled the room. In the center of this circular space stood a small insulated platform. Upon it, supported by gleaming glass rods, stood a huge, hollow hemisphere, from which emanated an eery blue light. Coming closer and looking downward into it, Carl was thrilled to see moving objects, familiar outlines of buildings he knew belonged to that part of London called Piccadilly Circus. "This will explain the question you asked me earlier in the evening. The inventors of modern television would be envious if they knew of this creation. I need no transmitting station to bring into my home any scene I may desire." Pierre quickly removed his cape, and began tinkering with an assortment of strange knobs upon a large panel back of the bowl. The Piccadilly Circus scene disappeared, and into its place came a picture of Ruth's deserted apartment. Again Pierre turned the knobs, and the scene in the bowl became a moving panorama of London streets. Swiftly they passed, until the estate of the Countess Moonard appeared in the strange vessel.