“Enough,” said Dr. Banks, with sudden vagueness. “I’m so sorry that you’ve been walking around thinking that our test meant we had a treatment. Until we know for sure what’s attacking these people, we can’t put forth a viable course of antiparasitics, and we don’t want to risk a mass panic.”

“Why not? Are you afraid that it would hurt your stock prices?”

“No, Sally, we’re afraid that it would hurt everyone who trusts our brand enough to have one of our implants. The SymboGen Intestinal Bodyguard was created to mitigate the worst effects of the hygiene hypothesis. It allowed us to undo, in a single step, literally decades of excessive sterilization and reduced microbial diversity. Since then, the implants have become responsible for everything from maintaining insulin levels in diabetics to controlling issues with human brain chemistry and secreting natural birth control. They represent millions of dollars saved in pharmacological costs annually. That doesn’t even take into account the savings they naturally cause in the areas of preventative medicine and allergy control. They’ve changed the face of medicine.”

“And?” I asked.

“And if you take all that away, even assuming that every single host was able to survive the course of antibiotics necessary to flush both the implant and the unknown protozoa from their system, what infrastructure is going to be there to step up and take care of all these people’s medical needs? Who is going to be standing by with the pills no one is in the habit of taking anymore, the shots no one wants to give themselves? What happens to the women who live in regions where birth control is unfairly restricted, but have been getting around that by buying their implants out of state? Suddenly they’re back in the bad old position of needing to find a way to convince their doctors they’re not immoral whores just because they want to be allowed to control their own reproduction. Take away the implants, and the medical system of this country crumbles.” There was a strange new light in Dr. Banks’s eyes. He sounded appropriately solemn as he was speaking, but something about his expression was almost… proud. “That’s just America. D. symbogenesis is a global phenomenon. What do you say to the people who are finally able to control their own medical destinies? How do you convince them to throw away their miracle because they might, potentially, come into contact with another type of parasite someday, and it could hurt them?”

“Oh.” I bit my lip, worrying it between my teeth before asking, “But how does that excuse not sharing the test with the authorities? I mean, you could tell them everything, just the way you told me, and then show them how to check for the bad parasites, and they’d be able to… I don’t know, quarantine people when they started getting sick. Maybe then, no one would get hurt just because they got too close to someone who was already going to die.” I thought of Devi, who’d only wanted to be sure that her wife was okay. Would putting Katherine under quarantine as soon as she tested positive have made any difference? Probably not. But we would never know, would we?

“We could also trigger a panic, leading to millions of people overdosing on antiparasitics as they become convinced that D. symbogenesis is somehow connected to the outbreaks. We’re already starting to see resource hoarding in some areas where the sleepwalkers have been especially active.” Dr. Banks shook his head. “We set out to become the first name in parasites. Well, we achieved it. Now we have to be careful, or the sins of an entire biological genus will be heaped upon our heads.”

“You mean your head,” I said.

Dr. Banks blinked. Apparently, declarative statements were more surprising than bewildered questions. “What do you mean?”

“I mean Dr. Jablonsky is dead, and Dr. Cale is missing, so any blame is going to fall on you. Is that why you look so tired?” I tried to sound sympathetic. I wasn’t sure that it was working.

For his part, Dr. Banks looked even more surprised than he had before. “I wasn’t aware you knew so much about SymboGen’s history.”

“Everyone knows about SymboGen’s history,” I said. It was true: he’d made sure we couldn’t forget it. I just knew a little more than I was meant to. “I didn’t read the books, but they’re available in audio. I listened to them while I was at work. There was a lot I wanted to understand.”

“Ah, yes, work,” said Dr. Banks, suddenly looking like he was back on familiar ground. “Will tells me that you haven’t been to the shelter in more than a week. Have you been feeling unwell?”

SymboGen got me the job at the shelter. Of course Dr. Banks would be on a first-name basis with my boss. “I was at home,” I said. “Nathan and I got caught in an outbreak in Lafayette.”

“Oh, yes, I heard about that,” said Dr. Banks. “Whatever were you doing out there?”

Fortunately, I had a believable, if utterly frivolous excuse for what we would have been doing out in Lafayette: “There’s this ice cream company called Jeni’s? They’re from Ohio? Anyway, the only place in the Bay Area that carries most of their flavors is Diablo Foods in Lafayette. I wanted ice cream, and Nathan felt like indulging me, I guess.” I bit my lip again. “Maybe we should have just gone to Ghirardelli Square.”

“Maybe you should have,” Dr. Banks agreed. “Sally, I am so, so sorry you had to see that.”

There was one question I hadn’t asked yet. I sniffled again, doing my best to look pitiful, and asked, “If the sleepwalking sickness is because of a proto-whatsit, not the implants, how is it messing up everyone’s behavior? I mean. I know some parasites can get into the brain, but don’t those have to be bigger? Not so tiny that they can get through water filters?”