‘You really didn’t put that there?’ Caplan asked, clearly reluctant to abandon his original hypothesis: that Nasim had inserted herself into a map of Cambridge sights and attractions as an inconspicuous way to solicit bribes from wealthy anorexics.

‘Believe me,’ she said, ‘a bunny rabbit is not an accurate representation of my mood right now.’ She started to close the door, but Caplan held up one skinny arm and took hold of the edge.

‘I’m sure you’ll want to talk about this again,’ he said. ‘Once you’ve thought it over.’

‘I’m sure I won’t.’

‘Just give me your email address.’

‘Absolutely not.’ Nasim increased her pressure on the door and he started yielding.

‘You can always reach me through my blog!’ he panted. ‘Overpowering Falsehood dot com, the number one site for rational thinking about the future-’

He pulled his hand free just in time to avoid having it squashed between the door and the jamb. Nasim locked the door and waited in the hallway, checking through the peephole until he gave up and walked away. She went to her room and summoned the Cambridge map on her own phone. Caplan’s version hadn’t been a hoax; the inane rabbit was there, exactly as before. Somehow it had been written into the map’s public database.

Who had done this to her? How? Why? Was it a prank, or something nastier? She started mentally listing names and pondering motives, then caught herself. Instead of drifting off into a paranoid fantasy, she needed to gather some solid information.

Nasim took her phone and walked three blocks down the street. After a delay of a minute or so, the rabbit icon on the map moved to match her new position. She walked further, to a small park. Once the rabbit had caught up, she switched off the phone. Back in the house, she checked the map again, via her laptop. The rabbit was still in the park.

So nobody had disclosed her home address, as such – but her phone had taken it upon itself to broadcast her location in real-time to the world.

Using the landline, she called the department’s IT support.

‘This is Christopher, how can I help you?’

‘My name’s Nasim Golestani. I’m with Professor Redland’s group.’

‘Okay; what’s the problem?’

She explained the situation. Christopher sank into a thoughtful silence that lasted almost half a minute. Then he said, ‘You know AcTrack?’

‘No.’

‘Sure you do. It’s a reality-mining plug-in that learns about academic networking using physical proximity, along with email and calling patterns. Last semester we put it on everyone’s phones.’

The phones were supplied by the department, to ensure that everyone had compatible software; Nasim just accepted all the upgrades they sent out without even looking at them.

‘All right,’ she said, ‘so I’m running AcTrack. Is everyone else who’s running AcTrack appearing on Google Maps?’

‘No,’ Christopher conceded, ‘but you know Tinkle?’

‘No.’

‘It’s a new femtoblogging service going through a beta trial.’

‘Femtoblogging?’

‘Like microblogging, only snappier. It tells everyone in your network where you are and how you’re feeling, once a minute. Tinkle are working on ways of extracting mood and contactability data automatically from non-invasive biometrics, but that part’s not implemented yet.’

‘But why am I running it at all,’ Nasim asked wearily, ‘and why is it telling complete strangers where I am?’

‘Oh, I doubt you’re actually running a Tinkle client,’ Christopher said. ‘But on the server side, AcTrack and Tinkle are both application layers that run on a lower-level platform called Murmur. It’s possible that there’s been some glitch with Murmur – maybe a server crash that was improperly recovered and ended up corrupting some files. Tinkle does hook into Google Maps, and though it shouldn’t be putting anyone on the public database, if you don’t belong to any Tinkle Clan it might have inadvertently defaulted you to public.’

Nasim digested this. ‘So what’s the solution?’

‘I’ll contact the company that administers Murmur and see if they can get to the bottom of the problem, but that might take a while. In the meantime, you could try shutting down AcTrack; that won’t take you off the map, but it should stop the location updates.’

Following his instructions, Nasim interrupted the phone’s usual boot sequence to enter a set-up mode where she could disable AcTrack. She checked the map again. The rabbit was still present – and still proclaiming her identity – but even though the phone was switched on, the icon hadn’t moved from the park back to her house. She wouldn’t get any more door-knockers.

She thanked Christopher and hung up. The whole bizarre episode had fractured her mood; the TV and the blogs had lost their hypnotic attraction. She paced the living room, agitated. People who might have sat beside her in a classroom fifteen years before were facing batons, water-cannon and bullets. The sheer fatuousness of her own tribulations made her life here seem like a mockery.

So, what was she supposed to do? Jump on a plane to Tehran and get herself arrested at the airport? She and her mother had departed illegally; they didn’t even have Iranian passports any more. And as far as she could tell, her adopted country was already following the best possible course: keeping its grubby fingers right out this time. And if they weren’t, she doubted that the CIA was prepared to take advice from her.

The truth was, she had nothing to contribute. Whatever happened, it would all unfold without her.

Nasim picked up her phone and found the menu option for ‘I’m not as sick as I thought, I’m coming in after all.’

Instead of the usual reassuring tone confirming success, there was a disapproving buzz and an alert popped up.

‘AcTrack plug-in disabled,’ it read. ‘Unable to complete this function.’

John Redland’s group had the twelfth floor of Building 46 all to themselves. From her corner of the lab, Nasim could peer across Vassar Street at the Stata Centre, an apparition out of a cartoon fairy-tale with its façade of tilted surfaces intersecting at vertiginous angles. As an architect’s sketch or computer model it must have looked enchanting, but in real life this gingerbread house had developed all manner of leaks, cracks and snow-traps.

Nasim turned back to her computer screen, where a tentative wiring map for part of the brain of a zebra finch was slowly taking form. The map wasn’t based on any individual bird, nor was it the product of any single technique. Some of the finches who’d contributed to it had been genetically engineered so that their neurons fluoresced under UV light, with each cell body glowing in a random colour that made it stand out clearly from its neighbours; that was the famous Lichtman-Livet-Sanes ‘Brainbow’ technique, developed over at Harvard. Others had had their brains bathed in cocktails of synthetic molecules – tagged with distinctive radioisotopes – that were taken up only by cells bearing receptors for particular neurotransmitters. A third cohort had been imaged after selective labelling, with monoclonal antibodies, of the cellular adhesion molecules that bound one neuron to another. And a fourth set of birds had been subject to no chemical interventions at all, and simply had their brains peeled by an ATLUM – an Automatic Tape-collecting Lathe Ultra Microtome – into fine slices which could then be imaged by electron microscopes and reassembled in three dimensions.

Altogether, nearly a thousand finches had lived and died to create the map that lay in front of her. Nasim hadn’t personally touched a feather on their heads, though she’d watched her colleagues operating, injecting and dissecting. None of the procedures carried out on the living birds should have left them in pain, and with decent-sized cages, plenty of food and access to mates, their lives probably hadn’t been much more stressful than they would have been in the wild. Nasim was never sure exactly where she’d draw the line, though. If it had been a thousand chimpanzees instead, for a project equally distant from any urgent human need, she didn’t know if she would have found a way to rationalise it, or if she would have walked away.