"Yes," he said thoughtfully. "I think we'll explore it. But I don't really expect we'll find any life here. There's nothing outside to see but a single metal mast. We've got some signal lights on our hull. If we're careful--" No one objected. The appearance of the asteroid was utterly disappointing. Its lifelessness and its obliviousness to their coming and their calls were worse than disappointing. There was nothing to be seen but a metal stick from which signals went out to nowhere. Burke jockeyed the little ship to the tunnel-mouth. It was fully a hundred feet in diameter. He turned on the ship's signal lights. Gently, cautiously, he worked down the very center of the very large bore. It was perfectly straight. They went in for what seemed an indefinite distance. Presently the signal lights showed that the wall was smoothed. The bore grew smaller still. They went on and on. Suddenly Keller grunted. He pointed to one of the six television screens which aimed out the length of the tunnel and showed the stars beyond. Those stars were being blotted out. Something vast moved slowly and deliberately across the shaft they navigated. It closed the opening. Their retreat was blocked. The ship was shut in, in the center of a mountain of stone which floated perpetually in emptiness. Burke checked the ship's forward motion, judging their speed by the side walls shown by the ship's outside lights. Very, very slowly, faint illumination appeared outside. In seconds they could see that the light came from long tubes of faint bluish light. The light changed. It grew stronger. It turned green and then yellowish and then became very bright, indeed. Then nothing more took place. Nothing whatever. The five inside the ship waited more than an hour for some other development, but absolutely nothing happened. Chapter 6 There was a tiny shock; in a minute, trivial contact of the ship with something outside it. Drifting within the now brightly lighted bore, it had touched the wall. There was no force to the impact. Keller made an interested noise. When eyes turned to him, he pointed to a dial. A needle on that dial pointed just past the figure "30." Burke grunted. "The devil! We've been waiting for things to happen, and they already have! It's our move." "According to that needle," agreed Holmes, "somebody has kindly put thirty point seven mercury inches of air-pressure around the ship outside. We can walk out and breathe, now." "If," said Burke, "it's air. It could be something else. I'll have to check it." He got out the self-contained diving apparatus that had been brought along to serve as a strictly temporary space suit. "I'll try a cigarette-lighter. Maybe it will burn naturally. Maybe it will go out. It could make an explosion. But I doubt that very much." "We'll hope," said Holmes, "that the lighter burns."