The Domino Pattern by Timothy Zahn

di -Master Strinni.”
    “Did Colix eat the same thing every day?” I asked.
    “I don’t think so.” Bayta said.
    “Then I can get the menu later.” Stepping over to the Shorshic rack, I picked up the top box.
    It was heavier than I’d expected, which probably meant it contained a complete meal instead of appetizers or desserts or something lighter. The box itself was made of a thin but sturdy plastic, sealed with a quick-release strip. Experimentally, I pulled the strip open a couple of centimeters and then tried to reseal it.
    It didn’t reseal. I tried it again, just to be sure, then tried lifting the corner of the lid, hoping to get a look at the food inside.
    But there was a wide flap in the way, and pulling on the corner merely gained me another couple of centimeters of open strip. “I presume the Spiders would have noticed if one of the meals had shown up unsealed?”
    “Of course,” Bayta said. “Aren’t you going to open it?”
    “No need,” I said, looking closely at the box in search of punctures or small tears. “What happens to the boxes once the food’s been served? Do they get flattened and stored somewhere for reuse?”
    “No, they go directly into the recycling system,” she said. “The fibers are designed to serve as a catalyst for some of the waste breakdown.”
    “When you say directly, you mean…?”
    “I mean directly,” she said, frowning. “Yesterday’s packages are already gone. What do you mean, no need ? I thought you wanted to check the food for contamination.”
    “I do.” I confirmed. “Or rather, I did. But it’s clear now that if the food was tampered with, it didn’t happen at the kitchen where these things were cooked and packaged. It happened right here aboard the train.” I grimaced. “And it happened on purpose.”
    Her eyes went wide. “Are you saying they were murdered ?”
    “I don’t see any way around it,” I said. “One death might be an accident. But not two. Not like this.”
    “But Dr. Witherspoon said Shorshians are especially susceptible to poisoning.”
    “Exactly my point,” I said. “Even small amounts of poisons typically generate obvious symptoms in that species. If Colix and Bofiv had ingested the stuff gradually, over the past few days, the symptoms would have shown up long ago. The only conclusion is that they were both nailed with large, lethal doses, all at once. That kind of dosage doesn’t usually happen by accident.”
    For another few seconds Bayta remained silent. But I could see the shock fading from her face as she realized I was making sense. “All right,” she said slowly. “But why would anyone want to kill them?”
    “I haven’t the faintest,” I conceded. “Actually, it’s worse than that. We don’t even know yet that they were specifically targeted.”
    Her eyes did the widening thing again. “You mean the killings might have been random?”
    “Or the killer was aiming at someone else and missed,” I said. “But one thing at a time. The easiest method for delivering poison is by food or drink, since everybody eats and nine out of ten people don’t pay that much attention to their food while they’re eating it.”
    “Yes,” Bayta said thoughtfully. “Shorshic meals usually include a common dipping dish, don’t they?”
    “That’s what the cultural profiles say,” I confirmed. “Which would certainly make surreptitious tampering easier. The downside is that the poisoner pretty much has to be in the same group as the victim—a stranger leaning in so he can sprinkle fairy dust into a dipping dish in the middle of the table would be a little obvious.”
    “But if the poisoner was also a Shorshian, wouldn’t he run the risk of being poisoned himself?” Bayta asked.
    “Absolutely,” I said. “Which is one of several intriguing questions about this whole thing. Namely, were both Colix and Bofiv murdered by a third party? Or could Bofiv have murdered Colix and then gotten caught in his own