Free Probability Sun by Nancy Kress

dying with the colony skeeter, had been captured alive. But if they did, they weren’t getting him back.
    *   *   *
    “Tell me again,” Marbet Grant said to Lyle Kaufman as they waited at the security checkpoint in the deep gut of the Alan B. Shepard . She closed her eyes.
    Watching her, Kaufman understood. It wasn’t that Marbet wanted to hear the information again because she hadn’t understood it. She wanted to hear it again as a mantra, a calming device, a stream of known words. After this last checkpoint, nothing would be known.
    He said, “The theory—and it is only theory—is that the Fallers have a strong, overriding instinct to eliminate any ‘others’ that could present any danger to themselves. It’s an evolutionary strategy that may have worked and been reinforced over eons on their home planet, which we know has high cosmic bombardment and thus may have yielded many, many mutations. They simply wiped out anything, including their own children, that were too different.
    “At the first sign of any otherness, a Faller seems to go into something like human instinctive fear of falling—a xenophobia way beyond what humans usually feel. Although nobody is sure, there may be only one surviving, genetically similar group of Fallers. No races, few permitted variant alleles. Anything else arouses hostility, including us.”
    “The ultimate committers of hate crimes,” Marbet murmured. She still had not opened her eyes. After a moment she added, “I’ve never met any alien.”
    He shouldn’t be surprised, Kaufman thought. She’d never been out of the Solar System, and no other aliens in the known galaxy except Fallers had invented space travel. Or even the steam engine.
    “All right,” Marbet said, opening her eyes, “I’m ready.”
    Kaufman thumbed open the door.
    The Faller’s cage was ten meters wide by twenty meters long. The length was divided by an invisible, two-molecule-thick plastic sheet separating the Faller’s atmosphere from the human one. The barrier conducted sound almost perfectly. Behind it the Faller was bound naked against the far wall, which was padded so that the alien could not injure itself, no matter what it did.
    Not “it,” Kaufman reminded himself. The xenobiologists, none of whom at Marbet’s request were present, had decided that the Faller was male, although not for any reason apparent to Kaufman. The alien was about a meter and a half tall, covered with hairless tough hide of deep brown. Short powerful legs. An equally powerful tail on which he balanced at rest. A torso like a barrel, with three incongruously slim “arms” that seemed all flexible tentacle, each ending in a hand with three fingers and an opposable thumb. No claws or nails. The head, although roughly the size of a human head, was far more cylindrical. Two eyes, no visible nostrils (they were located under the chin), a large mouth.
    At first sight of them, the Faller bared sharp long teeth.
    Marbet did not react. She walked to the barrier and sat down cross-legged in front of it, looking upward at the alien. A posture of submission, Kaufman decided, and wondered if that was a good idea with a species that wiped out anything it didn’t like.
    “You can leave if you like, Lyle,” Marbet said over her shoulder. “I’m going to be here for a few days, and there won’t be anything to see.”
    A few days ? “You mean … sleeping and eating here?”
    “Yes. And I’ll need a chamber pot.” And then, not rising, Marbet began removing her clothes.
    “Do you … do you want me to take those away?”
    “No. Leave them right here, along with everything else you bring me. Food, utensils, bedding. Also an erasable tablet and pen—not a computer or holostage, please—and a music cube.”
    “All right,” Kaufman said. Marbet was now removing her underclothes. Her body, genemod perfect, gave Kaufman a sudden lamentable erection. The alien was still baring its teeth. Kaufman left to find the