My back was a solid knot of tension as I forced myself to sit up, undo my seat belt, and open the car door. I started to stand, only to fall to the ground as my knees refused to bear my weight, sending me sprawling. Nathan ran toward me.

“Sal! Are you all right?”

“I’m fine.” I grasped his offered hand, using it to pull myself back to my feet. My palms and knees were stinging. Gravel had cut through my skin, leaving the heels of my hands red and raw. I laughed a little, wincing at the faint edge of hysteria in the sound. “Let’s remember to grab the first aid kit, okay?”

“Okay,” said Nathan, keeping hold of my hand as he kicked the passenger-side door shut and started toward the building entrance.

I let him lead, and focused on listening as hard as I could to our environment, looking for any sign that we were not alone. I could hear cars driving by, and the distant sound of sirens—but that didn’t necessarily mean anything. We were far enough away from the bridge exit that I couldn’t be hearing those sirens, and San Francisco is a city with a lot of sirens. Police cars, private security, ambulances, they all made up the constant background noise of the city. I was probably just hearing one of those, and not a sign that the crisis was getting worse in our immediate vicinity.

A thin line of ice curled and uncurled in my belly, almost like a new kind of parasite. You don’t really believe that, murmured that little inner voice, and it was right. I knew the situation was devolving around us, and we didn’t have very long. Maybe pressuring Dr. Cale into letting us go home had been the wrong thing to do… but we couldn’t leave the dogs. They needed us, and unless the world was burning, that wasn’t a trust that I was willing to break.

There were no moans on the thin, smoke-scented air. Even if the mob of sleepwalkers was spreading, it either wasn’t here yet, or it wasn’t attacking yet. We had a little bit of time.

Nathan got the door unlocked and tugged me inside. I let go of his hand and took the lead down the hallway to the stairs. We didn’t even discuss using the elevator. The mob by the bridge had drawn the fragility of our situation into sharp relief, and the last thing that either of us wanted was to be trapped between floors if the electricity suddenly cut out.

The stairwell was silent save for the soft clicks of our shoes against the steps, and the sound of Nathan’s faintly labored breathing after the third floor. Neither of us was in the best of shape, but at least my tendency to walk when I couldn’t get a bus somewhere meant that I did all right with things like “walking up eight flights of stairs.” By the time we reached our floor, his face had taken on a distressingly plummy cast, and he wasn’t talking anymore, just nodding when I looked back and asked if he was all right. I paused on the landing, my hand on the door handle, and waited for him to catch up.

“I don’t think we should go through until you catch your breath,” I said. “We don’t know what’s up there.” Nathan’s building had a limited number of apartments per floor, and most were occupied by single residents or couples, rather than entire families. I wasn’t certain how many people we shared the floor with, but I knew that it was less than ten. That was a good thing, because most of them were also young urban professionals, the kind of people who thought that no price was too high to pay for the opportunity to avoid needing to take a sick day. The kind of people the SymboGen implant had been virtually designed for. If they had started their cascade into sleepwalker-dom…

We would cross that bridge when we came to it. “My life made a lot more sense a week ago,” I said, almost contemplatively.

Nathan looked at me, his hands braced on his knees and his black hair lank with sweat. It hung into his eyes, making him look disheveled. “I don’t think either of us has had a life that made sense in years,” he said. “We’ve just started noticing how strange everything is.”

“The broken doors are open,” I said sourly.

“Come and enter and be home,” Nathan replied. “Open the door, Sal. I’m okay to keep moving.”

I wanted to argue with him. I wanted to tell him that we needed to take a few more minutes so that he could catch his breath and I could prepare myself for whatever was waiting in the hall. And I knew how much I hated it when people argued with me about my own assessment of my mental or physical state, so I didn’t say anything. I just nodded, once, and opened the door.

The man standing on the other side was almost an anticlimax. He was barefoot, and his pants were unfastened, like he had been in the process of getting dressed when his thoughts became scrambled and unclear. His mouth hung slack, although he wasn’t drooling. There was no one behind him: the hallway was empty and beckoning, promising safety and lockable doors, if we could just get past the poor soul who was staring blankly at us.

“Hi,” I said. It wasn’t a good start. I couldn’t think of anything else to do.

The man twitched. Not a lot—I wouldn’t even have noticed it in someone like Nathan or Dr. Cale, who still moved like the living, all heat and suddenness—but enough that it was clear he was responding to my voice. His eyes refocused on my face, vague interest sparking in their depths. My breath caught, my lungs seeming to constrict like collapsing balloons. He knew I was there. He could hear me.

“Sal…” said Nathan. His voice was low, marbled with amazement and fear. Amazement because this man knew I was speaking to him somehow: fear because we both knew what the sleepwalkers could do.