On this voyage it had been used to contain an assortment of botanical specimens from a planet seventy light-years beyond Regulus. They were on their way to the botanical research laboratory on Cassim. As a routine precaution they'd been placed in the hospital, which could be fumigated when they were taken out. Now the doctor had piled them in one side of the compartment, which he had divided in half with a transparent plastic sheet. He stayed in that side. Kathy occupied the other. She had some flowering plants to look at and admire. They'd come from the air room and she was delighted with their coloring and beauty. But Doctor Nordenfeld had put them there as a continuing test for chlorophage. If Kathy carried that murderous virus on her person, the flowering plants would die of it--probably even before she did. It was a scrupulously scientific test for the deadly stuff. Completely sealed off except for a circulator to freshen the air she breathed, Kathy was settled with toys and picture books. It was an improvised but well-designed germproof room. The air for Kathy to breathe was sterilized before it reached her. The air she had breathed was sterilized as it left her plastic-sided residence. It should be the perfection of protection for the ship--if it was not already too late. The vision-phone buzzed. Doctor Nordenfeld stirred in his chair and flipped the switch. The _Star Queen's_ skipper looked at him out of the screen. "I've cut the overdrive," said the skipper. "The passengers haven't been told." "Very sensible," said the doctor. "When will we know?" "That we can go on living? When the other possibility is exhausted." "Then, how will we know?" asked skipper stonily. Doctor Nordenfeld ticked off the possibilities. He bent down a finger. "One, her father took great pains. Maybe he did manage an aseptic transfer from a germ-free room to Altaira. Kathy may not have been exposed to the chlorophage. If she hasn't, no bleached spots will show up on the air-room foliage or among the flowering plants in the room with her. Nobody in the crew or among the passengers will die." He bent down a second finger. "It is probably more likely that white spots will appear on the plants in the air room _and_ here, and people will start to die. That will mean Kathy brought contagion here the instant she arrived, and almost certainly that Altaira will become like Kamerun--uninhabited. In such a case we are finished." * * * * * He bent down a third finger. "Not so likely, but preferable, white spots may appear on the foliage inside the plastic with Kathy, but not in the ship's air room. In that case she was exposed, but the virus was incubating when she came on board, and only developed and spread after she was isolated. Possibly, in such a case, we can save the passengers and crew, but the ship will probably have to be melted down in space. It would be tricky, but it might be done."