'Andrea,' he said, sounding slurred and drunk and too loud, even to his own ears.

  She turned and met his eyes. There was a slight pause before she smiled, and when she did, the smile wasn't quite right, as if she'd been asked to hold it too long for a photograph.

  'Hello, Mick. I was beginning to think--'

  'It's okay.' He forced out each word with care, making sure it came out right before moving to the next. 'I just had some second thoughts.'

  'I don't blame you. How does it feel?'

  'A bit odd. It'll get easier.'

  'Yes, that's what they told me.' She took another sip from the coffee holder, even though it must have been empty. They were standing about two metres apart, close enough to talk, close enough to look like two friends or colleagues who'd bumped into each other around the lake.

  'It's really good of you--' Mick began.

  Andrea shook her head urgently. 'Please. It's okay. We talked it over. We both agreed it was the right thing to do. If the tables were turned, you wouldn't have hesitated.'

  'Maybe not.'

  'I know you, Mick. Maybe better than you know yourself. You'd have done all that you could, and more.'

  'I just want you to know . . . I'm not taking any of this lightly. Not you having to see me, like this . . . not what he has to go through while I'm around.'

  'He said to tell you there are worse ways to spend a week.'

  Mick tried to smile. He felt the muscles of his face move, but without a mirror there was no way to judge the outcome. The moment stretched. A football splashed into the lake and began to drift away from the edge. He heard a little boy start crying.

  'Your hair looks different,' Mick said.

  'You don't like it.'

  'No, I do. It really suits you. Did you have that done after . . . oh, wait. I see. You were on your way to the salon.'

  He could see the scratch on her face where she'd grazed it on the kerb, when the car knocked her down. She hadn't even needed stitches. In a week it would hardly show at all.

  'I can't begin to imagine what it's been like for you,' Andrea said. 'I can't imagine what this is like for you.'

  'It helps.'

  'You don't sound convinced.'

  'I want it to help. I think it's going to. It's just that right now it feels like I've made the worst mistake of my life.'

  Andrea held up the coffee holder. 'Do you fancy one? It's my treat.'

  Andrea was a solicitor. She worked for a small legal firm located in modern offices near the park. There was a Starbucks near her office building. 'They don't know me there, do they?'

  'Not unless you've been moonlighting. Come on. I hate to say it, but you could use some practice walking.'

  'As long as you won't laugh.'

  'I wouldn't dream of it. Hold my hand, Mick. It'll make it easier.'

  Before he could step back, Andrea closed the distance between them and took his hand in hers. It was good of her to do that, Mick thought. He'd been wondering how he would initiate that first touch, and Andrea had spared him the fumbling awkwardness that would almost certainly have ensued. That was Andrea to a T, always thinking of others and trying to make life a little easier for them, no matter how small the difference. It was why people liked her so much; why her friends were so fiercely loyal.

  'It's going to be okay, Mick,' Andrea said gently. 'Everything that's happened between us . . . it doesn't matter now. I've said bad things to you and you've said bad things to me. But let's forget about all that. Let's just make the most of what time we have.'

  'I'm scared of losing you.'

  'You're a good man. You've more friends than you realise.'

  He was sweating in the heat, so much so that the glasses began to slip down his nose. The view tilted towards his shoes. He raised his free hand in a stiff, salute-like gesture and pushed the glasses back into place. Andrea's hand tightened on his.

  'I can't go through with this,' Mick said. 'I should go back.'

  'You started it,' Andrea said sternly, but without rancour. 'Now you finish it. All the way, Mick Leighton.'

  TUESDAY

  Things were much better by the morning of the second day. When he woke in Joe Liversedge's lab there was a fluency in his movements that simply hadn't been there the evening before, when he'd said goodbye to Andrea. He now felt as if he was inhabiting the host body, rather than simply shuffling it around like a puppet. He still needed the glasses to be able to see anything, but the nervelink was conveying sensation much more effectively now, so that when he touched something it came through without any of the fuzziness or lag he'd been experiencing the day before. Most tourists were able to achieve reasonable accuracy of touch differentiation within twenty-four hours. Within two days, their degree of proprioceptive immersion was generally good enough to allow complex motor tasks such as cycling, swimming or skiing. Repeat-visit tourists, especially those that went back into the same body, got over the transition period even faster. To them it was like moving back into a house after a short absence.

  Joe's team gave Mick a thorough check-up in the annexe. It was all routine stuff. Amy Flint, Joe's senior graduate student, insisted on adding some more numbers to the tactile test database she was building for the study. That meant Mick sitting at a table, without the glasses, being asked to hold various objects and decide what shape they were and what they were made of. He scored excellently, only failing to distinguish between wood and plastic balls of similar weight and texture. Flint was cheerfully casual around him, without any of the affectedness or oversensitivity Mick had quickly detected in his friends and colleagues. Clearly she didn't know what had happened; she just thought Joe had opted to go for a different test subject than himself.

  Joe was upbeat about Mick's progress. Everything, from the host body to the hardware, was holding up well. The bandwidth was stable at nearly two megabytes per second, more than enough spare capacity to permit Mick the use of a second video feed to peer back into the version of the lab on the other side. The other version of Joe held the cam up so that Mick could see his own body, reclining on the heavy-duty immersion couch. Mick had expected to be disturbed by that, but the whole experience turned out to be oddly banal, like replaying a home movie.

  When they were done with the tests, Joe walked Mick over to the university canteen, where he ate a liquid breakfast, slurping down three containers of fruit yoghurt. While he ate - which was tricky, but another of the things that was supposed to get easier with practice - he gazed distractedly at the television in the canteen. The wall-sized screen was running through the morning news, with the sound turned down. At the moment the screen was showing grainy footage of the Polish miners, caught on surveillance camera as they trudged into the low, concrete pithead building on their way to work. The cave-in had happened three days ago. The miners were still trapped underground, in all the worldlines that were in contact with this one, including Mick's own.

  'Poor fuckers,' Joe said, looking up from a draft paper he was pencilling remarks over.

  'Maybe they'll get them out.'

  'Aye. Maybe. Wouldn't fancy my chances down there, though.'

  The picture changed to a summary of football scores. Again, most of the games had ended in identical results across the contacted worldlines, but two or three - highlighted in sidebars, with analysis text ticking below them - had ended differently, with one team even being dropped from the rankings.

  Afterwards Mick walked on his own to the tram stop and caught the next service into the city centre. Already he could feel that he was attracting less attention than the day before. He still moved a little stiffly, he could tell that just by looking at his reflection in the glass as he boarded the tram, but there was no longer anything comical or robotic about it. He just looked like someone with a touch of arthritis, or someone who'd been overdoing it in the gym and was now paying with a dose of sore muscles.

  As the tram whisked its way through traffic, he thought back to the evening before. The meet
ing with Andrea, and the subsequent day, had gone as well as he could have expected. Things had been strained at first, but by the time they'd been to Starbucks, he had detected an easing in her manner, and that had made him feel more at ease as well. They'd made small talk, skirting around the main thing neither of them wanted to discuss. Andrea had taken most of the day off; she didn't have to be at the law offices until late afternoon, just to check that no problems had arisen in her absence.

  They'd talked about what to do with the rest of their day together.

  'Maybe we could drive up into the Beacons,' Mick had said. 'It'll be nice up in the hills with a bit of a breeze. We always used to enjoy those days out.'

  'Been a while though,' Andrea had said. 'I'm not sure my legs are up to it any more.'

  'You always used to hustle up those hills.'

  'Emphasis on the "used to", unfortunately. Now I get out of breath just walking up Saint Mary's Street with a bag full of shopping.'

  Mick looked at her sceptically, but he couldn't deny that Andrea had a point. Neither of them was the keen, outdoors type they had been when they met fifteen years earlier through the university's hill-walking club. Back then they'd spent long weekends exploring the hills of the Brecon Beacons and the Black Mountains, or driving to Snowdonia or the Lake District. They'd had some hair-raising moments together, when the weather turned against them or when they suddenly realised they were on completely the wrong ridge. But what Mick remembered, more than anything, was not being cold and wet, but the feeling of relief when they arrived at some cosy warm pub at the end of the day, both of them ravenous and thirsty and high on what they'd achieved. Good memories, all of them. Why hadn't they kept it up, instead of letting their jobs rule their weekends?

  'Look, maybe we might drive up to the Beacons in a day or two,' Andrea said. 'But I think it's a bit ambitious for today, don't you?'

  'You're probably right,' Mick said.

  After some debate, they'd agreed to visit the castle and then take a boat ride around the bay to see the huge and impressive sea defences up close. Both were things they'd always meant to do together but had kept putting off for another weekend. The castle was heaving with tourists, even on this midweek day. Because a lot of them were nervelinked, though, they afforded Mick a welcome measure of inconspicuousness. No one gave him a second glance as he bumbled along with the other shade-wearing bodysnatchers, even though he must have looked considerably more affluent and well fed than the average mule. Afterwards, they went to look at the Roman ruins, where Rachel Liversedge was busy talking to a group of bored primary school children from the valleys.

  Mick enjoyed the boat ride more than the trip to the castle. There were still enough nervelinked tourists on the boat for him not to feel completely out of place, and being out in the bay offered some respite from the cloying heat of the city centre. Mick had even felt the breeze on the back of his hand, evidence that the nervelink was really bedding in.

  It was Andrea who nudged the conversation towards the reason for Mick's presence. She'd just returned from the counter with two paper cups brimming with murky coffee, nearly spilling them as the boat swayed unexpectedly. She sat down on the boat's hard wooden bench.

  'I forgot to ask how it went in the lab this morning,' she said brightly. 'Everything working out okay?'

  'Very well,' Mick said. 'Joe says we were getting two megs this morning. That's as good as he was hoping for.'

  'You'll have to explain that to me. I know it's to do with the amount of data you're able to send through the link, but I don't know how it compares with what we'd be using for a typical tourist set-up.'

  Mick remembered what Joe had told him. 'It's not as good. Tourists can use as much bandwidth as they can afford. But Joe's correlators never get above five megabytes per second. That's at the start of the twelve-day window too. It only gets worse by day five or six.'

  'Is two enough?'

  'It's what Joe's got to work with.' Mick reached up and tapped the glasses. 'It shouldn't be enough for full-colour vision at normal resolution, according to Joe. But there's an awful lot of clever software in the lab to take care of that. It's constantly guessing, filling in gaps.'

  'How does it look?'

  'Like I'm looking at the world through a pair of sunglasses.' He pulled them off his nose and tilted them towards Andrea. 'Except it's the glasses that are actually doing the seeing, not my - his - eyes. Most of the time, it's good enough that I don't notice anything weird. If I wiggle my head around fast - or if something streaks past too quickly - then the glasses have trouble keeping up with the changing view.' He jammed the glasses back on, just in time for a seagull to flash past only a few metres from the boat. He had a momentary sense of the seagull breaking up into blocky areas of confused pixels, as if it had been painted by a cubist, before the glasses smoothed things over and normality ensued.

  'What about all the rest of it? Hearing, touch . . .'

  'They don't take up anything like as much bandwidth as vision. The way Joe puts it, postural information only needs a few basic parameters: the angles of my limb joints, that kind of thing. Hearing's pretty straightforward. And touch is the easiest of all, as it happens.'

  'Really?'

  'So Joe says. Hold my hand.'

  Andrea hesitated an instant then took Mick's hand.

  'Now squeeze it,' Mick said.

  She tightened her hold. 'Are you getting that?'

  'Perfectly. It's much easier than sending sound. If you were to say something to me, the acoustic signal would have to be sampled, digitised, compressed and pushed across the link: hundreds of bytes per second. But all touch needs is a single parameter. The system will still be able to keep sending touch even when everything else gets too difficult.'

  'Then it's the last thing to go.'

  'It's the most fundamental sense we have. That's the way it ought to be.'

  After a few moments, Andrea said, 'How long?'

  'Four days,' Mick said slowly. 'Maybe five, if we're lucky. Joe says we'll have a better handle on the decay curve by tomorrow.'

  'I'm worried, Mick. I don't know how I'm going to deal with losing you.'

  He closed his other hand on hers and squeezed in return. 'You'll get me back.'

  'I know. It's just . . . it won't be you. It'll be the other you.'

  'They're both me.'

  'That's not how it feels right now. It feels like I'm having an affair while my husband's away.'

  'It shouldn't. I am your husband. We're both your husband.'

  They said nothing after that, sitting in silence as the boat bobbed its way back to shore. It was not that they had said anything upsetting, just that words were no longer adequate. Andrea kept holding his hand. Mick wanted this morning to continue for ever: the boat, the breeze, the perfect sky over the bay. Even then he chided himself for dwelling on the passage of time, rather than making the most of the experience as it happened to him. That had always been his problem, ever since he was a kid. School holidays had always been steeped in a melancholic sense of how few days were left.

  But this wasn't a holiday.

  After a while, he noticed that some people had gathered at the bow of the boat, pressing against the railings. They were pointing up, into the sky. Some of them had pulled out phones.

  'There's something going on,' Mick said.

  'I can see it,' Andrea answered. She touched the side of his face, steering his view until he was craning up as far as his neck would allow. 'It's an aeroplane.'

  Mick waited until the glasses picked out the tiny, moving speck of the plane etching a pale contrail in its wake. He felt a twinge of resentment towards anyone still having the freedom to fly, when the rest of humanity was denied that right. It had been a nice dream while it lasted, flying. He had no idea what political or military purpose the plane was serving, but it would be an easy matter to find out, were he that interested. The news would be in all the papers by the afternoon. The plane wouldn't just be overflying
this version of Cardiff, but his as well. That had been one of the hardest things to take since Andrea's death. The world at large steamrolled on, its course undeflected by that single human tragedy. Andrea had died in the accident in his world, she'd survived unscathed in this one, and that plane's course wouldn't have changed in any measurable way (in either reality).

  'I love seeing aeroplanes,' Andrea said. 'It reminds me of what things were like before the moratorium. Don't you?'

  'Actually,' Mick said, 'they make me a bit sad.'

  WEDNESDAY

  Mick knew how busy Andrea had been lately, and he tried to persuade her against taking any time off from her work. Andrea had protested, saying her colleagues could handle her workload for a few days. Mick knew better than that - Andrea practically ran the firm single-handedly - but in the end they'd come to a compromise. Andrea would take time off from the office, but she'd pop in first thing in the morning to put out any really serious fires.