It was time for a diversion. I was familiar with the PREDPREY code. I knew the swarms were programmed to pursue moving targets if they seemed to be fleeing from them. What would make a good target?

I cocked my arm, and threw the black dissection kit high into the air, in the general direction of the second swarm. The kit landed on edge, and tumbled across the ground for a moment. Immediately, the second swarm began to go after it.

At the same moment, the first swarm moved away from the door, also pursuing the kit. It was just like a dog chasing a ball. I felt a moment of elation as I watched it go. It was, after all, just a programmed swarm. I thought: This is child's play. I hurried toward the door. That was a mistake. Because apparently my hasty movement triggered the swarm, which immediately stopped, and swirled backward to the door again, blocking my path. There it remained, pulsing streaks of silver, like a blade glinting in the sun. Blocking my path.

It took me a moment to realize the significance of that. My movement hadn't triggered the swarm to pursue me. The swarm hadn't chased me at all. Instead it had moved to block my way. It was anticipating my movement.

That wasn't in the code. The swarm was inventing new behavior, appropriate to the situation. Instead of pursuing me, it had fallen back and trapped me.

It had gone beyond its programming-way beyond. I couldn't see how that had happened. I thought it must be some kind of random reinforcement. Because the individual particles had very little memory. The intelligence of the swarm was necessarily limited. It shouldn't be that difficult to outsmart it.

I tried to feint to the left, then the right. The cloud went with me, but only for a moment. Then it dropped back to the door again. As if it knew that my goal was the door, and by staying there it would succeed.

That was far too clever. There had to be additional programming they hadn't told me about. I said into the headset, "What the hell have you guys done with these things?" David: "It's not going to let you get past, Jack."

Just hearing him say that irritated me. "You think so? We'll see." Because my next step was obvious. Close to the ground like this, the swarm was structurally vulnerable. It was a cluster of particles no larger than specks of dust. If I disrupted the cluster-if I broke up its structure-then the particles would have to reorganize themselves, just as a scattered flock of birds would re-form in the air. That would take at least a few seconds. And in that time I would be able to get through the door.

But how to disrupt it? I swung the stick in my hand, hearing it whoosh through the air, but it was clearly unsatisfactory. I needed something with a much bigger flat surface, like a paddle or a palm frond-something to create a large disrupting wind… My mind was racing. I needed something.

Something.

Behind me, the second cloud was closing in. It moved toward me in an erratic zigzag pattern, to cut off any attempt I might make to run past it. I watched with a kind of horrified fascination. I knew that this, too, had never been coded in the program. This was self-organized, emergent behavior-and its purpose was only too clear. It was stalking me. The pulsing sound grew louder as the swarm came closer and closer.

I had to disrupt it.

Turning in a circle, I looked at the ground all around me. I saw nothing I could use. The nearest juniper tree was too far away. The cholla cactuses were flimsy. I thought, of course there's nothing out here, it's the fucking desert. I scanned the exterior of the building, hoping someone had left out an implement, like a rake…

Nothing.

Nothing at all. I was out here with nothing but the shirt on my back, and there was nobody that could help me toOf course!

The headset crackled: "Jack, listen…"

But I didn't hear any more after that. As I pulled my shirt over my head, the headset came away, falling to the ground. And then, holding the shirt in my hand, I swung it in broad whooshing arcs through the air. And screaming like a banshee, I charged the swarm by the door.

The swarm vibrated with a deep thrumming sound. It flattened slightly as I ran toward it, and then I was in the midst of the particles, and plunged into an odd semidarkness, like being in a dust storm. I couldn't see anything-I couldn't see the door-I groped blindly for the doorknob-and my eyes stung from the particles, but I kept swinging my shirt in broad whooshing arcs, and in a moment the darkness began to fade. I was dispersing the cloud, sending particles spinning off in all directions. My vision was clearing, and my breathing was still okay, though my throat felt dry and painful. I began to feel thousands of tiny pinpricks all over my body, but they hardly hurt.

Now I could see the door in front of me. The doorknob was just to my left. I kept swinging my shirt, and suddenly the cloud seemed to clear entirely away, almost as if it was moving out of range of my disruption. In that instant I slipped through the door and slammed it shut behind me. I blinked in sudden darkness. I could hardly see. I thought my eyes would adjust from the glare of sunlight, and I waited a moment, but my vision did not improve. Instead, it seemed to be getting worse. I could just make out the glass doors of the airlock directly ahead. I still felt the stinging pinpricks all over my skin. My throat was dry and my breathing was raspy. I coughed. My vision was dimming. I started to feel dizzy.

On the other side of the airlock, Ricky and Mae stood watching me. I heard Ricky shout, "Come on, Jack! Hurry!"

My eyes burned painfully. My dizziness grew rapidly worse. I leaned against the wall to keep from falling over. My throat felt thick. I was having difficulty breathing. Gasping, I waited for the glass doors to open, but they remained closed. I stared stupidly at the airlock. "You have to stand in front of the doors! Stand!"

I felt like the world was in slow motion. All my strength was gone. My body felt weak and shaky. The stinging was worse. The room was getting darker. I didn't think I could stand up on my own.

"Stand! Jack!"

Somehow, I shoved away from the wall, and lurched toward the airlock. With a hiss, the glass doors slid open.

"Go, Jack! Now!"

I saw spots before my eyes. I was dizzy, and sick to my stomach. I stumbled into the airlock, banging against the glass as I stepped inside. With every second that passed it was harder to breathe. I knew I was suffocating.

Outside the building, I heard the low thrumming sound start up again. I turned slowly to look back.

The glass doors hissed shut.

I looked down at my body but could barely see it. My skin appeared black. I was covered in dust. My body ached. My shirt was black with dust, too. The spray stung me, and I closed my eyes. Then the air handlers started up, whooshing loudly. I saw the dust sucked off my shirt. My vision was clearer, but I still couldn't breathe. The shirt slipped from my hand, flattening against the grate at my feet. I bent to reach down for it. My body began to shake, tremble. I heard only the roar of the handlers.

I felt a wave of nausea. My knees buckled. I sagged against the wall. I looked at Mae and Ricky through the second glass doors; they seemed far away. As I watched, they receded even farther, moving away into the distance. Soon they were too far away for me to worry any longer. I knew I was dying. As I closed my eyes, I fell to the ground, and the roar of the air handlers faded into cold and total silence.