He went into his hut, switched on the radiolite, and stood staring at a door he had not opened for a long time. With a little sigh he pushed at the latch. The smell of musty rot drifted out. A lamp revealed a complete medical laboratory, one that had not, apparently, been used for months at least. Garth almost dropped a bottle as he fumbled it from the shelf. Cursing, he opened the rotgut Ganymedean whiskey and poured it down his throat. That helped. Steadied somewhat, he went to work. The Noctoli pollen antitoxin was still here, but it might have lost its efficacy. He tested it. Good. It seemed strong, the antibodies having a long life-cycle. It would work. Garth packed a compact medical kit. After that he stood for quite a while staring at two blank spaces on the wall, where pictures had once hung. Moira and Doc Willard. _Damn!_ Garth snatched up the liquor and fled the house. He fought his way along the steep path that led to the Tor's summit. The physical exertion was a relief. * * * * * At the top, he sat down, his back against a rock. Beneath him lay Oretown, yellow-blue lights winking dimly. In a cleared field some distance away was the ovoid shape of the spaceship that had brought Paula and Brown--the _Hunter_. To the west, across sandy desert, lay Chahnn, dead city that had once housed an incredibly-advanced science--lost now, its people dust. Northwest, beyond distant ridges, was the Black Forest, unexplored, secret, menacing. Six years ago Dr. Jem Willard had come to Ganymede with his intern, Ed Garth. Willard was trying to discover the cure for the Silver Plague that was wrecking Earth. He would have found it--he had got on the track. But-- An emergency call had come in one night. A native needed an appendectomy. Willard couldn't fly a plane. He had called on Garth, and Garth had been drunk. But he had piloted the plane anyhow. The crack-up happened over the Black Forest. That was the last thing Garth remembered, or almost the last. It would have been more merciful if the oblivion had been complete. Months later he staggered out of the Forest into Oretown, alone. The Noctoli poison had almost erased his experiences from his mind. He could remember a bare cell where he and Willard had been prisoned--that, and one other thing. A picture of Doc Willard stretched on an altar, while Garth lifted a gleaming, razor-sharp knife above his friend's breast. He remembered that, but no more. It was enough. The question burning in his brain had nearly wrecked his sanity. He had tried to get back into the Black Forest, to find Willard, dead or alive, to learn what had happened--to discover the answer to his problem. He had failed. A year later he learned that his fiancée, Moira, had died of the Silver Plague. And he knew that Willard might have saved her, had he lived and continued his research. After that, Ed Garth hit the skids. He went down fast, stopping only when he reached the bottom.