Greg Egan - Quarantine

As for some backyard operator engineering a vector that's both compatible with existing nanomachines and infectious enough to constitute a threat… such a feat is no doubt every bit as implausible as factoring a megadigit code key by pure good luck.

The crowd thins out around me; the sky darkens. The world goes on as always. It all adds up to normality. Lui's had the mod since two; for all I know he might have released it already. How long would it take to spread? He'll have made one minor change from the version Po-kwai received: inhibiting the collapse won't be an option, requiring conscious invocation; the unwitting users will have no choice. With ten thousand, or a hundred thousand people smeared, how long before their smeared selves learn to suppress the collapse of the rest of the city? And with twelve million people smeared —

I look up at the sky, and catch sight of a faint point of light above the fading glow in the west. I stare at it for ten long seconds, before I realize it's only Venus.

The woman at Third Hemisphere frowns and says, 'You're early. Come back in two hours.'

'Speed it up. I'll pay you — '

She laughs. 'You can pay me whatever you like, it won't make any difference. The machine's been programmed, it's building your nanomachines; nothing's going to "speed it up" now.'

Nothing? What if I paid her to leave me alone with the synthesizer, then smeared — and didn't collapse until I had Ensemble installed in my head, allowing me to choose the whole sequence of events to have taken place in some 'impossibly' short time? There'd be no risk of the machine's accelerated action resulting in a defective mod … since if the mod turned out to be defective, the miraculous acceleration would never have taken place.

Or would it? What if I introduced some subtle flaw which didn't manifest itself immediately? I stare at the silent machine — which looks disconcertingly like an upmarket beverage dispenser — and I baulk at the prospect of having it stray from the safety of known probabilities. It's already juggling with matter on a molecular scale, subject to quantum uncertainties; I don't want it rendered capable of spitting out anything at all. Ensemble is my only advantage; if I take short cuts and screw it up, I'll have no chance whatsoever of finding Lui in time.

I say, 'I'll wait outside. Call me, the instant — ' The woman nods, amused. 'You sound like an expectant father.'

I should prime; go into stake-out mode and pass the time effortlessly … but some part of me violently resists the idea. To prime, now, would be irresponsible, escapist, unnatural …

I contemplate this alien rhetoric numbly, more bemused than horrified. I've escaped the grip of the loyalty mod by collapsing in some unlikely way — did I expect to end up perfectly unchanged in every other respect? Perhaps an increased distaste for neural mods was a necessary — or highly probable — concomitant of wanting to be set free.

So I wait like a human: sick with pointless, unproductive fears. Trying to imagine the unimaginable. If the whole planet smeared, permanently … what exactly would people experience? Nothing — because there is no collapse to make anything real? Or everything — because there is no collapse to make anything less than real? Everything, separately — one isolated consciousness per eigenstate, like the many-worlds model brought to life? Or everything, simultaneously — a cacophony of superimposed possibilities? What I've been through myself — or at least those memories which have survived the collapse — might bear no resemblance to the nature of things when there'll be no collapse at any future time. Once there's nothing to make the past unique, the whole experience could be radically different. Whatever the case, I'm certain of one thing: Lui can't be allowed to succeed. I only hope that my smeared self agrees.

The Third Hemisphere woman doesn't ask what it is I'm so desperate to try. I transfer the money. She hands me the vial, and I use it at once.

She says, 'I hope we'll do business again.'

I stop pinching my nostril. 'I doubt that very much.'

I sniff twice. A drop of fluid falls to the floor.

As I walk out of the alley, I instruct MindTools to notify me when Ensemble proclaims its existence. The expert system predicted two to three hours for installation, depending on the contingencies of the user's neural anatomy.

Back on the main road, the shopfronts are dazzling with holograms of merchandise; photorealism is out of style this year, and everything from shoes to cooking pots is rendered incandescent. I reach up and pass my hand back and forth through the spinning front wheel of a bicycle hovering two metres above the pavement, half expecting a shock of pain from the white-hot spokes.

I stand awhile, watching the crowd. I could still buy my way out of this. In two hours, I could be on the other side of the world. Maybe Laura was wrong; maybe whatever happens here could be confined, somehow. Once it's clear that there's an epidemic, if they closed the borders …

Against people who can tunnel through any kind of barrier? What do I think they're going to do? Drop the city into a black hole? Build their own Bubble?

Karen says, 'You stole the mod once; you can do it again. What does Lui have to stop you that BDI didn't?'

'And if he's already released the Endamoeba?'

'You don't know he's done that.'

'I don't know he hasn't.'

I stare up at the sky, and fight down a wave of vertigo.

The truth is, The Bubble has never confined us; it's merely rendered our confinement visible. The shock was not one of limitation; the shock was being forced to confront the alternative, the infinite freedom beyond.

I say, 'I think I'm getting Bubble Fever.'

Karen shakes her head. 'Bubble Fever,' she says, 'has gone right out of fashion.'

I have no choice but to wait for Ensemble — but that's no reason to delay preparing the tools I'm going to need to help me find Lui, once the mod is functional. Back in my flat, I write a small von Neumann program which will accept a six-digit number as input, consult Deja Vu's geographical database, and generate a map reference to a forty-five-metre square of dry land, somewhere in the city. It takes me a while to decide what else to rule out, besides water; there are plenty of land-use categories that seem 'obviously' pointless to search — too exposed, too inaccessible, or just plain ludicrous — but I can't decide where to draw the line, so I end up keeping most of them in. Airport runways are excluded, but any versions of me sent to investigate some corner of a rugby field or sewage treatment plant will just have to live with the knowledge that they probably won't see out the night.

I stare at the map in my head and think: By morning, this city is going to be smothered with my invisible corpses. And to the sole inheritor of my past, the 'miraculous' survivor of one more collapse … these deaths will seem less real than ever.

They're real to me, though. They're in my future, all of them.

The message flashes up, just before midnight: [MindTools: Broadcast received.

Sender ID: Ensemble (Third Hemisphere, $80,000).

Category: Autogenesis completion.]

I try to invoke it, but no interface window, no control panel, appears in my mind's eye — which is no great surprise; this mod isn't mine to use. So I sit on the bed and invoke Hyper nova, and bring back to life the being that Ensemble was made for.

What did Laura's spokesperson call him? Childlike? Unreliable? And if he's made of a billion endlessly dividing versions of me, what am I to him? A microscopic nonentity — as a single blood cell, or a single neuron, is to me? But then, there's no doubt that I'm forced to respect the needs of my blood cells and neurons, en masse. I've swayed him a hundred times before; surely one more miracle isn't unthinkable — especially when I'm so sure that I'm almost unanimous in wanting it. What versions of me could possibly wish for Lui to succeed?