Pam stared and asked questions, at first soothing ones. But presently she was saying indignantly, "I do believe it! That's near the place where I smelled fresh air!" Of course, fresh air in the asteroid, two hundred and seventy million miles from Earth, was as impossible as what Sandy had seen. Holmes came in presently, depressed and tired. He'd been filling his mind with the contents of black cubes. He knew how cooking was done in the kitchens of the fortress, some eons since. He knew how to prepare for inspection of the asteroid by a high-ranking officer. He was fully conversant with the bugle-calls once used in the fortress in the place of a public-address loud-speaker system. But he'd found no hint of how the fortress received its supplies, nor how the air was freshened, nor how reinforcements of men used to reach the asteroid. He was discouraged and vexed and weary. "Sandy," said Pam challengingly, "saw a live bird, bigger than a goose, in the gravity-machine room." Holmes shrugged. "Keller's fidgeting," he observed, "because he thinks he's seen movements in the vision-plates that show different inside views of this thing. But he isn't sure that he's seen anything move. Maybe we're all going out of our minds." "Then Joe's closest," said Pam darkly. "He worries about Sandy!" "And very reasonably," said Holmes tiredly. "Pam, this business of figuring that there's something deadly on the way and nothing to do about it--it's got me down!" He slumped in a chair. Pam frowned at him. Sandy sat perfectly still, her hands clenched. Burke came back twenty minutes later. His expression was studiedly calm. "I've found out where the garrison went," he said matter-of-factly. "I'm afraid we can't get any help from them. Or anybody else." Sandy looked at him mutely. He was completely self-controlled, and he did not look like a man resolutely refusing to despair, but Sandy knew him. To her it seemed that his eyes had sunk a little in his head. "Apparently there's nobody left on the world the garrison came from," said Burke in the tone of someone saying perfectly commonplace things, "so they didn't go back there and there's no use in our trying to make a contact with that world. This was an outpost fortress, you know. It was reached from somewhere far away, and carved out and armed to fight an enemy that didn't attack it for itself, but to get at the world or worlds that made it." He continued with immoderate calm, "I believe the home world of that civilization has two moons in its sky and something off at the horizon that looks like a hill, but isn't." "But--"