. . . Until you try to climb one of the emergency maintenance shafts. Then you know about it.

The ladder rungs are anchored to the antispinward wall of the shaft, rising toward the infinity of darkness that swallows my flashlight beam whenever I look up. Below me there's a long drop to a floor as unforgiving as the rocks at the foot of that waterfall. I climb steadily, pacing myself. The radius of curvature of the hab segments in YFH-Polity is small enough that if this is a single cylinder, it must be several kilometers in diameter. The roof of our hab is too high to touch from on top of a four-story building—the tallest structures in downtown—but I'm already far above that, with no sign of any openings.

At two hundred rungs I stop and rest. My arms are already feeling sore, muscles complaining. If I hadn't been working out for weeks, I'd be half-dead by now. I have no way of knowing how much farther I'll have to climb, and a dull worry gnaws at my stomach. What if I'm wrong? I'm assuming YFH-Polity is what it appears to be—a bunch of hab sectors spliced together with T-gates, interleaved among other self-contained polity segments across a multiplicity of real-space habitats. But what if they've gone further than simply blocking access to the rest of the network? It used to be the glasshouse, after all. What if my embedded passenger got it critically wrong, and we're actually stranded in a single location? There might be no way out.

But I can't go back. Yourdon must have figured out I'm on the loose by now. He'll mobilize the zombies and hunt me down like a rat cornered by army ants. Sam will be alone, wondering what happened, getting lonelier and crazier and more depressed. Sooner or later Mick will get his hands on Cass again. Jen will continue to play her malignant head games with Alice and Angel. Fiore will slowly turn the entire community into festering hate-filled puppets dancing to the tune of a dark ages culture based on insecurity and fear. And I'm fairly certain I know what their game is.

This isn't an archaeology experiment, it's a psychological warfare laboratory. They're testing out their design for an emergent behaviorally controlled society. YFH-Polity is a prototype for the next generation of cognitive dictatorship. Because, when they surface to release their new and improved version of Curious Yellow upon an unsuspecting net, it won't be to install a crude censorship regime. The payload they're planning will subtly impose behavioral rules on its victims, and the resulting emergent society will be one designed for their exploitation. A future of Church every Sunday, sword and chalice on the altar, a pervert in every pulpit preaching betrayal and distrust. Score whores in your neighborhood twitching panopticon curtains to enforce an existential fascism—and that's just the beginning. If the population of unvaccinated loyal carriers that Yourdon and Fiore are breeding up are destined to be carriers of the next release of Curious Yellow, the whole of human space will end up looking like a bunch of postop cases from the surgeon-confessor's clinic.

I can't afford to fail.

Minutes trickle away in silence before I start moving again, putting one hand above the other, then one foot, then the next hand, then the next foot. Repeat five times, then rest five beats. Repeat five times, then rest five beats makes ten. Repeat that another nine times, and I'm a hundred rungs farther up this tube of torments. Morbid thoughts plague me. I could hit a patch of grease and slip. Or just . . . not reach the top. The rungs are about twenty centimeters apart. I'm nearing five hundred, now, a hundred meters straight up. I'd hit the bottom so fast I'd splash. (Banging off the ladder on the way down, of course, gently drifting in the grip of Coriolis force. If I'd remembered to bring a plumb bob and a long enough string, I could figure out roughly how large this hab cylinder is, but I didn't think that far ahead.) My shoulders and elbows ache like they're in a vise. I've spent ages pulling and pushing on that stupid weight machine in the basement, but there's a difference between a half-hour workout and hanging on for life. If I have another memory fugue, I'm toast. How high can I go? How far apart are the inhabitable decks? If I'm unlucky, it could be kilometers—

I can't fail; I owe it to what Lauro, Iambic-18, and Neual used to mean to me not to let this happen. If I forget, then it might as well never have happened. Memory is liberty.

Six hundred rungs and my arms are shrieking for mercy. My thigh muscles aren't too happy, either. I'm gritting my teeth and hoping for mercy when I see a shadow above me. I stop and pant for a while, studying the outline. Rectangular, set into the wall. Could it be? I resume climbing, doggedly putting one hand in front of the other until I get there, close to nine hundred rungs up.

The shadow turns out to be the entrance to a short human-height tunnel leading away from beside the ladder. It runs two meters into the wall, then there's a thick, curved pressure door with another handwheel set in it. I'm there! I'd dance for joy except my arms feel as if they'd fall off. I step into the tunnel and switch my big flashlight to candle mode, then sit down and lean back against the wall and close my eyes for a count of a hundred. I think I've earned it. Besides, I don't know what'll be waiting on the other side of the door.

My arms feel like rubber, but I don't dare hang around. After a couple of minutes I force myself to my feet and inspect the handwheel. It looks workable, but when I try to turn it, it won't budge. "Shit," I mutter aloud. These are desperate straits. Maybe if I had a lever, I think, then I remember the flashlight. It's a big aluminum bar with a light at one end. I stick it through the spokes of the wheel and lean my weight on it, pushing against the wall, putting everything I've got into trying to make the thing turn.

After a couple of minutes I admit to myself that the wheel is not going to budge. It occurs to me that the builders of this hab were hot on fail-safes—what if it isn't turning because there's hard vacuum on the other side? Either it's got a deadlock triggered by too high a pressure differential, or it's just been in vacuum for so long that it's welded shut. "Shit," I mutter again. This could be another of Yourdon and Fiore's half-assed security measures. What good does it do me to get into an access tunnel if the other floors are all open to space? Assuming they know about these access tunnels in the first place, of course.

I wipe the sweat from my face and lean against the wall. "Up or down?" I ask aloud, but nobody's answering. Down, at least there's another level with air. Up, and . . . well, there might be nothing. Or there might be a whole damn orbital habitat that the bad guys don't know about. I could step out into a city boulevard in Old Paradys, or the back of a brasserie in Zhang Li. If I get lucky. If I'm not just imagining those places.

I stow the big flashlight in my belt loop and head back toward the ladder. If I don't get somewhere in another thousand rungs, I'm going to have to rethink my escape plan. Two thousand rungs total will be nearly half a kilometer. If I'd realized I was in for something like this, I would have bought climbing equipment, a winch, even a rope I could sling around myself so I could rest on the ladder. I fantasize briefly about rocket packs and elevator cars. Then I grab the next rung and begin to climb again.

Another nine hundred rungs up the ladder I become half-certain that I'm going to die. My arms are screaming at me, and my left thigh has started threatening to cramp. I pause for breath, my heart hammering. It's like being on the cliff again. This hab has got to be kilometers in radius—the gravity here feels about the same as it did when I started out. I'm in a tube with Urth-standard gee, air: terminal velocity will be about eighty meters per second. If I were to let go, the Coriolis force would rub me against the ladder like a cheese grater at two hundred kilometers per hour, leaving a greasy red smear. I can keep climbing, sure, but how easy is it going to be to climb back down if I keep going up until I'm exhausted? Thinking about it, I'm not sure going down is any better than going up. Less lifting, but still flexing a left elbow that feels about twice the size it should be, hot and throbbing as I raise it—