"Don't move."

Something icy-cold coursed through my veins. I shuddered.

"Jack. Don't move. Just for a second, okay?"

Something cold, a cold liquid running up my arm. I opened my eyes. The light was directly overhead, glaring, greenish-bright; I winced. My whole body ached. I felt like I'd been beaten. I was lying on my back on the black counter of Mae's biology lab. Squinting in the glare, I saw Mae standing beside me, bent over my left arm. She had an intravenous line in my elbow. "What's going on?"

"Jack, please. Don't move. I've only done this on lab animals."

"That's reassuring." I lifted my head to see what she was doing. My temples throbbed. I groaned, and lay back.

Mae said, "Feel bad?"

"Terrible."

"I'll bet. I had to inject you three times."

"With what?"

"You were in anaphylactic shock, Jack. You had a severe allergic reaction. Your throat almost closed up."

"Allergic reaction," I said. "That's what it was?"

"Severe one."

"It was from the swarm?"

She hesitated for a moment, then: "Of course."

"Would nano-sized particles cause an allergic reaction like that?"

"They certainly could…"

I said, "But you don't think so."

"No, I don't. I think the nanoparticles are antigenically inert. I think you reacted to a coliform toxin."

"A coliform toxin…" My throbbing headache came in waves. I took a breath, let it out slowly. I tried to figure out what she was saying. My mind was slow; my head hurt. A coliform toxin.

"Right."

"A toxin from E. coli bacteria? Is that what you mean?"

"Right. Proteolytic toxin, probably."

"And where would a toxin like that come from?"

"From the swarm," she said.

That made no sense at all. According to Ricky the E. coli bacteria were only used to manufacture precursor molecules. "But bacteria wouldn't be present in the swarm itself," I said. "I don't know, Jack. I think they could be."

Why was she so diffident? I wondered. It wasn't like her. Ordinarily, Mae was precise, sharp. "Well," I said, "somebody knows. The swarm's been designed. Bacteria's either been designed in, or not."

I heard her sigh, as if I just wasn't getting it.

But what wasn't I getting?

I said, "Did you salvage the particles that were blown off in the airlock? Did you keep the stuff from the airlock?"

"No. All the airlock particles were incinerated."

"Was that a smart-"

"It's built into the system, Jack. As a safety feature. We can't override it."

"Okay." Now it was my turn to sigh. So we didn't have any examples of swarm agents to study. I started to sit up, but she put a gentle hand on my chest, restraining me. "Take it slowly, Jack."

She was right, because sitting up made my headache much worse. I swung my feet over the side of the table. "How long was I out?"

"Twelve minutes."

"I feel like I was beaten up." My ribs ached with every breath.

"You had a lot of trouble breathing."

"I still do." I reached for a Kleenex and blew my nose. A lot of black stuff came out, mixed with blood and dust from the desert. I had to blow my nose four or five times to clear it. I crumpled the Kleenex and started to throw it away. Mae held out her hand. "I'll take that."

"No, it's okay-"

"Give it to me, Jack."

She took the Kleenex and slipped it into a little plastic bag and sealed it. That was when I realized how stupidly my mind was working. Of course that Kleenex would contain exactly the particles I wanted to study. I closed my eyes, breathed deeply, and waited for the throbbing in my head to ease up a little. When I opened my eyes again the glare in the room was less bright. It almost looked normal.

"By the way," Mae said, "Julia just called. She said you can't call her back, something about some tests. But she wanted to talk to you."

"Uh-huh."

I watched Mae take the Kleenex bag and put it inside a sealed jar. She screwed down the lid tightly. "Mae," I said, "if there's E. coli in the swarm, we can find out by looking at that right now. Shouldn't we do that?"

"I can't right now. I will as soon as I can. I'm having a little trouble with one of the fermentation units, and I need the microscopes for that."

"What kind of trouble?"

"I'm not sure yet. But yields are falling in one tank." She shook her head. "It's probably nothing serious. These things happen all the time. This whole manufacturing process is incredibly delicate, Jack. Keeping it going is like juggling a hundred balls at once. I have my hands full." I nodded. But I was starting to think that the real reason she wasn't looking at the Kleenex was that she already knew the swarm contained bacteria. She just didn't think it was her place to tell me that. And if that's what was going on, then she never would tell me. "Mae," I said. "Somebody has to tell me what's going on here. Not Ricky. I want somebody to really tell me."

"Good," she said. "I think that's a very good idea." …

That was how I found myself sitting in front of a computer workstation in one of those small rooms. The project engineer, David Brooks, sat beside me. As he talked, David continuously straightened his clothes-he smoothed his tie, shot his cuffs, snugged his collar, pulled up the creases in his trousers from his thighs. Then he'd cross one ankle over his knee, pull up his sock, cross the other ankle. Run his hands over his shoulders, brushing away imaginary dust. And then start over again. It was all unconscious, of course, and with my headache I might have found it irritating. But I didn't focus on it. Because with every piece of new information David gave me, my headache got worse and worse.

Unlike Ricky, David had a very organized mind, and he told me everything, starting from the beginning. Xymos had contracted to make a micro-robotic swarm that would function as an aerial camera. The particles were successfully manufactured, and worked indoors. But when they were tested outside, they lacked mobility in wind. The test swarm was blown away in a strong breeze. That was six weeks ago.

"You tested more swarms after that?" I said.

"Yes, many. Over the next four weeks, or so."

"None worked?"

"Right. None worked."

"So those original swarms are all gone-blown away by the wind?"

"Yes."

"Which means the runaway swarms that we see now have nothing to do with your original test swarms."

"Correct…"

"They are a result of contamination…"

David blinked rapidly. "What do you mean, contamination?"

"The twenty-five kilos of material that was blown by the exhaust fan into the environment because of a missing filter…"

"Who said it was twenty-five kilos?"

"Ricky did."

"Oh, no, Jack," David said. "We vented stuff for days. We must have vented five or six hundred kilos of contaminants-bacteria, molecules, assemblers." So Ricky had been understating the situation again. But I didn't understand why he bothered to lie about this. After all, it was just a mistake. And as Ricky had said, it was the contractor's mistake. "Okay," I said. "And you saw the first of these desert swarms when?"

"Two weeks ago," David said, nodding and smoothing his tie.

He explained that at first, the swarm was so disorganized that when it first appeared, they thought it was a cloud of desert insects, gnats or something. "It showed up for a while, going here and there around the laboratory building, and then it was gone. It seemed like a random event."

A swarm appeared again a couple of days later, he said, and by then it was much better organized. "It displayed distinctive swarming behavior, that sort of swirling in the cloud that you've seen. So it was clear that it was our stuff."

"And what happened then?"