Save for the clutter about the grid-control building there were no structures, no dwellings, no houses or homes anywhere in view. There was no longer even a highway leading to the grid. Calhoun threw on the outside microphones and there was no sound except a thin keening of wind in the steelwork overhead. But presently one of the cattle made a mournful bellowing sound. Calhoun whistled as he went from one port to another. "Murgatroyd," he said meditatively on his second round, "you observe--if you observe--one of the consequences of human error. I still don't know where I am, because I doubt that starplates have ever been made from this solar system, and I didn't take one for comparison anyhow. But I can tell you that this planet formerly had a habitability rating of something like oh point oh, meaning that if somebody wanted to live here it would be possible but it wouldn't be sensible. But people did come here, and it was a mistake." He stared at a human figure, far away. It was a woman, dressed in shapeless, badly draping garments. She moved toward a clump of dark-coated cattle and did something in their midst. "The mistake looks pretty evident to me," added Calhoun, "and I see some possibilities I don't like at all. There is such a thing as an isolation syndrome, Murgatroyd. A syndrome is a complex of pathological symptoms which occur together as a result of some morbid condition. To us humans, isolation is morbid. You help me to endure it, Murgatroyd, but I couldn't get along with only your society--charming as it is--for but so long. A group of people can get along longer than a single man, but there is a limit for any small-sized group." "_Chee_," said Murgatroyd. "In fact," said Calhoun, frowning, "there's a specific health problem involved, which the Med Service recognizes. There can be partial immunity, but there can be some tricky variations. If we're up against a really typical case we have a job on hand. And how did these people get that dust-ring out in space? They surely didn't hang it out themselves!" He sat down and scowled at his thoughts. Presently he rose again and once more surveyed the icy landscape. The curious green pasture about the landing grid was highly improbable. He saw glaciers over-hanging this valley. They were giant ice rivers which should continue to flow and overwhelm this relatively sheltered spot. They didn't. Why not? * * * * * It was more than an hour before the spacephone clattered. When Calhoun threw the switch again a new voice came out of it. This was also a male voice, but it was high-pitched as if from tension. "_We've been talking about you_," said the voice. It quivered with agitation which was quite out of reason. "_You say you're Med Service. All right. Suppose you prove it!_" The landed Med Ship should be proof enough for anybody. But Calhoun said politely: "I have the regular identifications. If you'll go on vision, I'll show you my credentials."