"You forget," he interrupted. "Think back, Frank. That day you came here. And we showed you the models of the vehicle. There were four of them----" Then I remembered. Dr. Gryce had shown me four small models. One he had sent back into Time. A flash, like a dissipating puff of vapor it was gone into the Past; still here in Space above the taboret on which it was standing, but vanished with centuries of Time to hide it from my sight. Another of the models, with Time unchanged, Dr. Gryce had sent into Infinite Smallness. I remembered watching it dwindling; a speck, a pinhead, then invisible even to the microscope. Two of the models were left. Martt and Frannie, but seventeen years old then, had taken one into the garden. Had started it growing in size. I recalled our frantic efforts to check its growth, lest it demolish the house. This was the one in which Martt and Brett had gone to the giant world and in which Brett had returned alone to that distant part of our universe. One model had remained. I had never thought of it since. Martt was saying, ". . . and we still have that last model. Father kept it very carefully." Martt's smile was wistful with the memory. "I think he--Father--had a premonition that he would not live to carry out his purpose. . . . The model is here." He opened a locked steel box. Again I gazed silently at that small cube of milk-white metal--a cube the length of my forearm, with its tiny tower on top, its glasslike balcony, its windows and its doors. "It's all complete," said Martt. "And I know how to operate it." Frannie said with a touch of breathlessness, "For a month past, Father has been gathering the necessary instruments. And the supplies--you see he--he really thought he was going to live----" "We're all ready," Martt added. "We will increase this model to normal size. Load it with our supplies. We can start tomorrow, Frank." IV Five million light-years from Earth! Who of finite human mind can conceive such unfathomable distance! Yet, as I crouched on the floor of the vehicle gazing down at the radiance emerging from the black void which was our first sight of the Inner Surface, the distance had seemed no more than gigantic. We were, in size, many million times our Earthly stature. The tiny Earth, from our larger viewpoint, was a little orange spinning above us in the void--a mere one-twentieth light-year away. Martt, for all his youth, had proved competent. He had made the trip once before with Brett; he handled the vehicle carefully, and with skill. He said now, as we three crouched by the floor window, "We'll soon be down to the atmosphere, Frank. I'm checking our fall--we want no errors----" We were reversed in Time--holding very nearly at a single instant, so that on the Inner Surface the time now was the same as it had been when we left the Earth.