Quarantine

based on the very same shot. Her face is distinctive, but who knows what she looks like by now? No need for plastic surgery; a good synthetic-skin mask is all that’s required.

I lodge the ad again, for what it’s worth. If Laura was taken by accident, she’d be long dead by now—and I doubt that I’d ever find the body, let alone the people responsible. My only real hope is that, not only did her kidnappers have some obscure reason for deliberately abducting her, but whatever it was, it required them to do something riskier than merely locking her up, or slaughtering her.

Like smuggling her out of the country.

Getting Laura onto a plane would not be difficult. Her imbecility would be almost as easy to conceal as her face; there are dozens of illegal mods which could transform her into the walking puppet of a travelling companion, or even a semi-autonomous ‘robot’, capable of such rudimentary tasks as laughing and crying at all the right moments during the in-flight movie.

Faking an exit-visa record in the Foreign Affairs database is no big deal. It would vanish an hour or two later, and the airline’s files would also be appropriately amended. Foreign Affairs, Customs and the airlines are all being screwed blind, twenty-four hours a day, by a hundred different hackers—and, ironically, that’s what makes it possible, if you’re lucky, to trace an illegal traveller. Hackers may run rings around the target systems’ own archaic security, but they can’t avoid making their presence known to each other. In the process of capturing data essential for their own work, they can’t help capturing details of other violations in progress. Like all information, this is for sale.

Bella is acting as a broker for me, as well as providing some data of her own. I call her and download another batch. The relevance of any one heap of raw data is a matter of luck; the more you buy, the better the odds, but there’s no guarantee of success when the event you’re trying to trace took place (if at all) at an unknown airport, at an unknown time in the last five weeks.

Finding the fake exit visas is easy; the very fact that they have to be wiped to avoid (sluggish) official scrutiny betrays their existence in any time series of illicit snapshots of the database. The problem is finding Laura in the crowd; there are over one hundred illegal exits per week, nationwide. From the Hilgemann, I have her DNA signature, fingerprints, retinal patterns and skeletal measurements. DNA isn’t used by Customs (there are too many complications, legal and cultural, in sampling international travellers en masse), but the other three are always checked, and must match for pre-departure clearance. After that, though, the common practice is to change these details in the fake visa record, precisely to make things harder for people like me. Although the record itself must persist for the duration of the flight, with the name and photo unchanged (to avoid triggering various anti-terrorist checks carried out by the airlines), the biological ID data isn’t accessed again until the passenger goes through Customs at their destination. So, there are only two brief periods when the visa record needs to contain anything truthful; in theory, these times could be measured in milliseconds, but in practice things can’t be tuned that finely, and the windows have to be several minutes long. However, fingerprints and retinal patterns are relatively easy to alter by nanosurgery, leaving only the bone lengths to be trusted. They can be modified too, if you’re desperate, but nobody walks onto a plane straight after that kind of reconstruction, puppet or not—and travelling as an obvious invalid would be like carrying a sign around your neck.

I analyse the latest series of snapshots; in no time at all they prove as worthless as the rest.

I flip idly through the gigabytes of junk that I’ve accumulated, flight after flight from the country’s ten international airports, everything from menus to seating plans to… cargo manifests. Of course, Laura could have been sent as cargo, but it wouldn’t have been a very smart choice. All cargo is either X-rayed or manually inspected, so there’s only one kind of cargo that a human being can mimic: a human corpse. Achieving the resemblance would be no problem; drugs which shut down the metabolism for a couple of hours, without damage to the brain or any other organ, have been available for decades. What makes the method unattractive is the signal-to-noise ratio; the sheer number of illegal live passengers is itself a kind of camouflage, but only one or two corpses are flown out of the country each week.

Still, I have nothing better to do, so I search through the cargo records in the data I’ve collected so far, and come up with seven corpses.

The routine security X-rays taken of every passenger also provide the basis for computing the set of skeletal measurements used as an ID check. Corpses, though, aren’t checked for ID; as with any other cargo, the X-ray images (a stereoscopic pair) are simply inspected by eye, then stored in the manifest. It takes me half an hour to track down a copy of the algorithm used by the airports to compute bone lengths; it’s part of the X-ray machines’ firmware, separate from the main passenger systems, so it isn’t present in any of my stolen memory dumps. I wouldn’t have wanted to cobble together a version of my own; the mathematics for converting data from stereo pairs to three-dimensional coordinates may be trivial, but automating the identification of the various bones is not.

I run the program on my seven corpses, checking for a match to Laura’s data… and get seven consecutive negatives—perversely, just as I’m struck by a reason why the kidnappers might have chosen this path, after all. It’s conceivable that Laura’s brain damage prevented them from using a puppet mod; many off-the-shelf mods rely explicitly on the existence of certain neural structures which ‘everyone’ supposedly has in common, but which Laura might be lacking. No doubt any such problems could be circumvented, given time—but mapping Laura’s non- standard brain, and reprogramming the nanomachines accordingly, would be no trivial matter. Other solutions would have looked tempting.

The lack of a positive result rules out nothing; the X-rays in the cargo record could have been fudged, a few minutes after they were taken. Computerized information is as evanescent as the quantum vacuum, with virtual truths and falsehoods endlessly popping in and out of existence. Deceptions of any magnitude are possible, on a short enough time scale; laws only apply to data that sits still long enough to be caught out.

I skim through the X-ray analysis program, curious to see how it works, but the code for anatomical-feature recognition is pretty dull stuff, an interminable list of rules and exceptions, and the rest is a few lines of formulae. I had a faint, nagging doubt that differences in geometry between the cargo and passenger X-ray systems might have been giving me garbage results, but in fact all the relevant dimensions are stored along with the image pairs themselves, neatly tagged with standard descriptors, and the program takes nothing for granted.

Once the bone lengths have been computed, a match is declared if any discrepancies fall within an age- dependent tolerance limit, which makes allowance for the possibility of small changes since the visa was issued. This tolerance is highest, of course, for children and adolescents, and not much leeway is granted at Laura’s age— perhaps I should increase it? Customs may prefer to err on the side of false negatives, but I’d rather make the opposite mistake.

I realize my stupidity with a jolt: I’m still thinking in terms of passengers. A fake corpse doesn’t need to be ambulatory. No skeletal reconstruction, however crippling, can be ruled out—which leaves me without a single piece of data I can trust.

That’s not quite true. Most bones can be altered—if a period of convalescence is acceptable—but it’s next to impossible to mess with certain parts of the skull, without the tampering being both dangerous and obvious.

I modify the match criteria, stripping away all the other comparisons. When I run this new version, a matching record appears at once:

cargo id: 184309547 Flight: QANTAS 295

Departure: Perth, 13:06, December 23rd, 2067 Arrival: New Hong Kong, 14:22, December 23rd, 2067 Contents: Human remains [Han, Hsiu-lien]

Sender: New Hong Kong Consulate General 16 St George’s Terrace Perth 6000-0030016 Australia

Addressee: Wan Chei Funerals 132 Lee Tung Street Wan Chei 1135-0940132 New Hong Kong

A match on the basis of five skull measurements could be a coincidence. It could be deliberate misinformation. Why wouldn’t the kidnappers have altered the X-rays, wiping out even this hint of the truth?

I check the time the snapshot was taken. Twelve fifty-three. The cargo would have been X-rayed just two or three minutes before; you don’t risk changing data when a Customs officer might be staring right at it. Ten minutes later, though, and every trace of Laura Andrews would have been gone.

I shake my head, still suspicious. I don’t often get this lucky.

Karen leans over my shoulder and says, “That’s the definition of luck, you moron. Hurry