"You can tell me."

"Maybe on edge ... You getting any sleep?"

"Not much. Couple of hours."

"Maybe you should take a pill."

"I did. Doesn't seem to help. It's the damn pressure. I've been here a week now. This place gets to you."

"I imagine it must."

"Yeah. Well, anyway." He turned away, as if suddenly embarrassed. "Look, I'll be on the radio," he said. "I'll be with you every step of the way. I'm very grateful to you, Jack. You've brought sanity and order here. Just ... just be careful out there, okay?"

"I will."

Ricky stepped aside.

I went out the door past him.

Going down the hallway to the power station, with the air conditioners roaring full blast, Mae fell into step beside me. I said to her, "You really don't need to go out there, Mae. You could tell me over the radio how to handle the isotopes."

"It's not the isotopes I'm concerned with," she said, her voice low, so it would be buried in the roar. "It's the rabbit."

I wasn't sure I'd heard her. "The what?"

"The rabbit. I need to examine the rabbit again."

"Why?"

"You remember that tissue sample I cut from the stomach? Well, I looked at it under the microscope a few minutes ago."

"And?"

"I'm afraid we have big problems, Jack."

DAY 6

2:52 P.M.

I was the first one out the door, squinting in the desert sunlight. Even though it was almost three o'clock, the sun seemed as bright and hot as ever. A hot wind ruffled my trousers and shirt. I pulled my headset mouthpiece closer to my lips and said, "Bobby, you reading?"

"I read you, Jack."

"Got an image?"

"Yes, Jack."

Charley Davenport came out and laughed. He said, "You know, Ricky, you really are a stupid shmuck. You know that?"

Over my headset, I heard Ricky say, "Save it. You know I don't like compliments. Just get on with it."

Mae came through the door next. She had a backpack slung over one shoulder. She said to me, "For the isotopes."

"Are they heavy?"

"The containers are."

Then David Brooks came out, with Rosie close behind him. She made a face as she stepped onto the sand. "Jesus, it's hot," she said.

"Yeah, I think you'll find deserts tend to be that way," Charley said.

"No shit, Charley."

"I wouldn't shit you, Rosie." He belched.

I was busy scanning the horizon, but I saw nothing. The cars were parked under a shed about fifty yards away. The shed ended in a square white concrete building with narrow windows. That was the storage unit.

We started toward it. Rosie said, "Is that place air-conditioned?"

"Yes," Mae said. "But it's still hot. It's poorly insulated."

"Is it airtight?" I said.

"Not really."

"That means no," Davenport said, laughing. He spoke into his headset. "Bobby, what wind do we have?"

"Seventeen knots," Bobby Lembeck said. "Good strong wind."

"And how long until the wind dies? Sunset?"

"Probably, yeah. Another three hours."

I said, "That'll be plenty of time."

I noticed that David Brooks was not saying anything. He just trudged toward the building. Rosie followed close behind him.

"But you never know," Davenport said. "We could all be toast. Any minute now." He laughed again, in his irritating way.

Ricky said, "Charley, why don't you shut the fuck up?"

"Why don't you come out and make me, big boy?" Charley said. "What's the matter, your veins clogged with chicken shit?"

I said, "Let's stay focused, Charley."

"Hey, I'm focused. I'm focused."

The wind was blowing sand, creating a brownish blur just above the ground. Mae walked beside me. She looked across the desert and said abruptly, "I want to have a look at the rabbit. You all go ahead if you want."

She headed off to the right, toward the carcass. I went with her. And the others turned in a group and followed us. It seemed everybody wanted to stay together. The wind was still strong. Charley said, "Why do you want to see it, Mae?"

"I want to check something." She was pulling on gloves as she walked.

The headset crackled. Ricky said, "Would somebody please tell me what the hell is going on?"

"We're going to see the rabbit," Charley said.

"What for?"

"Mae wants to see it."

"She saw it before. Guys, you're very exposed out there. I wouldn't be waltzing around."

"Nobody's waltzing around, Ricky."

By now I could see the rabbit in the distance, partially obscured by the blowing sand. In a few moments, we were all standing over the carcass. The wind had blown the body over on its side. Mae crouched down, turned it on its back, laid open the carcass.

"Jeez," Rosie said.

I was startled to see that the exposed flesh was no longer smooth and pink. Instead, it was roughened everywhere, and in a few places looked as if it had been scraped. And it was covered by a milky white coating.

"Looks like it was dipped in acid," Charley said.

"Yes, it does," Mae said. She sounded grim.

I glanced at my watch. All this had occurred in two hours. "What happened to it?" Mae had taken out her magnifying glass and was bent close to the animal. She looked here and there, moving the glass quickly. Then she said, "It's been partially eaten."

"Eaten? By what?"

"Bacteria."

"Wait a minute," Charley Davenport said. "You think this is caused by Theta-d? You think the E. coli is eating it?"

"We'll know soon enough," she said. She reached into a pouch, and pulled out several glass tubes containing sterile swabs.

"But it's only been dead a short time."

"Long enough," Mae said. "And high temperatures accelerate growth." She daubed the animal with one swab after another, replacing each in a glass tube. "Then the Theta-d must be multiplying very aggressively."

"Bacteria will do that if you give them a good nutrient source. You shift into log phase growth where they're doubling every two or three minutes. I think that's what's happening here."

I said, "But if that's true, it means the swarm-"

"I don't know what it means, Jack," she said quickly. She looked at me and gave a slight shake of the head. The meaning was clear: not now.

But the others weren't put off. "Mae, Mae, Mae," Charley Davenport said. "You're telling us that the swarms killed the rabbit in order to eat it? In order to grow more coli? And make more nanoswarms?"

"I didn't say that, Charley." Her voice was calm, almost soothing. "But that's what you think," Charley continued. "You think the swarms consume mammalian tissue in order to reproduce-"

"Yes. That's what I think, Charley." Mae put her swabs away carefully, and got to her feet. "But I've taken cultures, now. We'll run them in Luria and agerose, and we'll see what we see."

"I bet if we come back in another hour, this white stuff will be gone, and we'll see black forming all over the body. New black nanoparticles. And eventually there'll be enough for a new swarm."

She nodded. "Yes. I think so, too."

"And that's why the wildlife around here has disappeared?" David Brooks said.

"Yes." She brushed a strand of hair back with her hand. "This has been going on for a while." There was a moment of silence. We all stood around the rabbit carcass, our backs to the blowing wind. The carcass was being consumed so quickly, I imagined I could almost see it happening right before my eyes, in real time.

"We better get rid of those fucking swarms," Charley said.

We all turned, and set off for the shed.

Nobody spoke.

There was nothing to say.

As we walked ahead, some of those small birds that hopped around the desert floor under the cholla cactus suddenly took to the air, chittering and wheeling before us. I said to Mae, "So there's no wildlife, but the birds are here?"

"Seems to be that way."

The flock wheeled and came back, then settled to the ground a hundred yards away. "Maybe they're too small for the swarms to bother with," Mae said. "Not enough flesh on their bodies."

"Maybe." I was thinking there might be another answer. But to be sure, I would have to check the code.

I stepped from the sun into the shade of the corrugated shed, and moved along the line of cars toward the door of the storage unit. The door was plastered with warning symbols-for nuclear radiation, biohazard, microwaves, high explosives, laser radiation. Charley said, "You can see why we keep this shit outside."

As I came to the door, Vince said, "Jack, you have a call. I'll patch it." My cell phone rang. It was probably Julia. I flipped it open. "Hello?"

"Dad." It was Eric. With that emphatic tone that he got when he was upset.

I sighed. "Yes, Eric."

"When are you coming back?"

"I'm not sure, son."

"Will you be here for dinner?"

"I'm afraid not. Why? What's the problem?"

"She is such an asshole."

"Eric, just tell me what the problem-"

"Aunt Ellen sticks up for her all the time. It's not fair."

"I'm kind of busy now, Eric, so just tell me-"

"Why? What are you doing?"

"Just tell me what's wrong, son."

"Never mind," he said, turning sulky, "if you're not coming home, it doesn't matter. Where are you, anyway? Are you in the desert?"

"Yes. How did you know that?"

"I talked to Mom. Aunt Ellen made us go to the hospital to see her. It's not fair. I didn't want to go. She made me anyway."

"Uh-huh. How is Mom?"

"She's checking out of the hospital."

"She's finished all her tests?"

"The doctors wanted her to stay," Eric said. "But she wants to get out. She has a cast on her arm, that's all. She says everything else is fine. Dad? Why do I always have to do what Aunt Ellen says? It's not fair."

"Let me talk to Ellen."

"She isn't here. She took Nicole to buy a new dress for her play."

"Who's with you at the house?"

"Maria."

"Okay," I said. "Have you done your homework?"

"Not yet."

"Well, get busy, son. I want your homework done before dinner." It was amazing how these lines just popped out of a parent's mouth.

By now I had reached the storage room door. I stared at all the warning signs. There were several I didn't know, like a diamond made up of four different colored squares inside, each with a number. Mae unlocked the door and went in.

"Dad?" Eric started to cry. "When are you coming home?"

"I don't know," I said. "I hope by tomorrow."

"Okay. Promise?"

"I promise."

I could hear him sniffling, and then through the phone a long snarff sound as he wiped his nose on his shirt. I told him he could call me later if he wanted to. He seemed better, and said okay, and then said good-bye.

I hung up, and entered the storage building.

The interior was divided into two large storage rooms, with shelves on all four walls, and freestanding shelves in the middle of the rooms. Concrete walls, concrete floor. There was another door in the second room, and a corrugated rollup door for truck deliveries. Hot sunlight came in through wood-frame windows. The air-conditioning rumbled noisily but, as Mae had said, the rooms were still hot. I closed the door behind me, and looked at the seal. It was just ordinary weather stripping. The shed was definitely not airtight. I walked along the shelves, stacked with bins of spare parts for the fabrication machinery, and the labs. The second room had more mundane items: cleaning supplies, toilet paper, bars of soap, boxes of cereal, and a couple of refrigerators filled with food. I turned to Mae. "Where are the isotopes?"

"Over here." She led me around a set of shelves, to a steel lid set in the concrete floor. The lid was about three feet in diameter. It looked like a buried garbage can, except for the glowing LED and keypad in the center. Mae dropped to one knee, and punched in a code quickly. The lid lifted with a hiss.

I saw a ladder that led down into a circular steel chamber. The isotopes were stored in metal containers of different sizes. Apparently Mae could tell which they were just by looking, because she said, "We have Selenium-172. Shall we use that?"

"Sure."

Mae started to climb down into the chamber.

"Will you fucking cut it out?" In a corner of the room, David Brooks jumped back from Charley Davenport. Charley was holding a big spray bottle of Windex cleaner. He was testing the squeeze trigger mechanism, and in the process spraying streaks of water on David. It didn't look accidental. "Give me that damn thing," David said, snatching the bottle away. "I think it might work," Charley said blandly. "But we'd need a remote mechanism." From the first room, Rosie said, "Would this work?" She held up a shiny cylinder, with wires dangling from it. "Isn't this a solenoid relay?"

"Yes," David said. "But I doubt it can exert enough force to squeeze this bottle. Has it got a rating? We need something bigger."

"And don't forget, you also need a remote controller," Charley said. "Unless you want to stand there and spray the fucker yourself."

Mae came up from below, carrying a heavy metal tube. She walked to the sink, and reached for a bottle of straw-colored liquid. She pulled on heavy rubber-coated gloves, and started to mix the isotope into the liquid. A radiation counter over the sink was chattering. Over the headset, Ricky said, "Aren't you guys forgetting something? Even if you have a remote, how are you going to get the cloud to come to it? Because I don't think the swarm will just come over and stand there while you hose it down."

"We'll find something to attract them," I said.

"Like what?"

"They were attracted to the rabbit."

"We don't have any rabbits."

Charley said, "You know, Ricky, you are a very negative person."

"I'm just telling you the facts."

"Thank you for sharing," Charley said.

Like Mae, Charley was seeing it, too: Ricky had dragged his feet every step of the way. It was as if Ricky wanted to keep the swarms alive. Which made no sense at all. But that's how he was behaving.

I would have said something to Charley about Ricky, but over our headsets everybody heard everything. The downside of modern communications: everybody can listen in. "Hey guys?" It was Bobby Lembeck. "How's it coming?"

"We're getting there. Why?"

"The wind's dropping."

"What is it now?" I said.

"Fifteen knots. Down from eighteen."

"That's still strong," I said. "We're okay."

"I know. I'm just telling you."

From the next room, Rosie said, "What's thermite?" In her hand she held a plastic tray filled with thumb-sized metal tubes.

"Careful with that," David said. "It must be left over from construction. I guess they did thermite welding."

"But what is it?"

"Thermite is aluminum and iron oxide," David said. "It burns very hot-three thousand degrees-and so bright you can't look directly at it. And it'll melt steel for welding."

"How much of that have we got?" I said to Rosie. "Because we can use it tonight."

"There's four boxes back there." She plucked one tube from the box. "So how do you set 'em off?"

"Be careful, Rosie. That's a magnesium wrapper. Any decent heat source will ignite it."

"Even matches?"

"If you want to lose your hand. Better use road flares, something with a fuse."

"I'll see," she said, and she disappeared around the corner.

The radiation counter was still clicking. I turned to the sink. Mae had capped the isotope tube. She was now pouring the straw-colored liquid into a Windex bottle. "Hey, guys?" It was Bobby Lembeck again. "I'm picking up some instability. Wind's fluctuating at twelve knots."

"Okay," I said. "We don't need to hear every little change, Bobby."

"I'm seeing some instability, is all."

"I think we're okay for the moment, Bobby."

Mae was going to be another few minutes, in any case. I went over to a computer workstation and turned it on. The screen glowed; there was a menu of options. Aloud, I said, "Ricky, can I put up the swarm code on this monitor?"

"The code?" Ricky said. He sounded alarmed. "What do you want the code for?"

"I want to see what you guys have done."

"Why?"

"Ricky, for Christ's sake, can I see it or not?"

"Sure, of course you can. All the code revisions are in the directory slash code. It's passworded."

I was typing. I found the directory. But I wasn't being allowed to enter it. "And the password is?"

"It's l-a-n-g-t-o-n, all lowercase."

"Okay."

I entered the password. I was now in the directory, looking at a list of program modifications, each with file size and date. The document sizes were large, which meant that these were all programs for other aspects of the swarm mechanism. Because the code for the particles themselves would be small-just a few lines, maybe eight, ten kilobytes, no more. "Ricky."

"Yes, Jack."

"Where's the particle code?"

"Isn't it there?"

"God damn it, Ricky. Stop screwing around."

"Hey, Jack, I'm not responsible for the archiving-"

"Ricky, these are workfiles, not archives," I said. "Tell me where."

A brief pause. "There should be a subdirectory slash C-D-N. It's kept there."

I scrolled down. "I see it."

Within this directory, I found a list of files, all very small. The modification dates started about six weeks ago. There was nothing new from the last two weeks. "Ricky. You haven't changed the code for two weeks?"

"Yeah, about that."

I clicked on the most recent document. "You got high-level summaries?" When these guys had worked for me, I always insisted that they write natural language summaries of the program structure. It was faster to review than documentation within the code itself. And they often solved logic problems when they had to write it out briefly. "Should be there," Ricky said.

On the screen, I saw:

/*Initialize*/

For j=1 to L x V do

Sj = 0 /*set initial demand to 0/

End For

For i=l to z do

For j = 1 to L x V do

ij = (state (x,y,z)) /*agent threshold param*/

? ij = (intent (Cj,Hj)) /*agent intention fill*/

Response = 0 /* begin agent response*/

Zone = z(i) /* intitial zone unlearned by agent*/

Sweep =1 /* activate agent travel*/

End For

End For

/*Main*/

For kl=1 to RVd do

For tm=1 to nv do