'Are you okay, Mick?'

  'I'm fine. Don't worry about me. It's these bloody shoes. I can't believe they ever fitted me.'

  He soldiered on for as long as he could, refusing to give in, but the going got harder and his pace slower. When he tripped again and this time grazed his shin through his trousers, he knew he'd pushed himself as far as he could go. Time was getting on. The mountain might as well have been in the Himalayas, for all his chances of climbing it.

  'I'm sorry. I'm useless. Go on without me. It's too nice a day not to finish it.'

  'Hey.' Andrea took his hand. 'Don't be like that. It was always going to be hard. Look how far we've come anyway.'

  Mick turned and looked dispiritedly down the valley. 'About three kilometres. I can still see the pub.'

  'Well, it felt further. And besides, this is actually a very nice spot to have the picnic.' Andrea made a show of rubbing her thigh. 'I'm about ready to stop anyway. Pulled a muscle going over that stile.'

  'You're just saying that.'

  'Shut up, Mick. I'm happy, okay? If you want to turn this into some miserable, pain-filled trek, go ahead. Me, I'm staying here.'

  She spread the blanket next to a dry brook and unpacked the food. The contents of the picnic basket looked very good indeed. The taste came through the nervelink as a kind of thin, diluted impression, more like the memory of taste rather than the thing itself. But he managed to eat without making too much of a mess, and some of it actually bordered on the enjoyable. They ate, listening to the birds, saying little. Now and then other walkers trudged past, barely giving Mick and Andrea a glance as they continued towards the hills.

  'I guess I shouldn't have kidded myself I was ever going to get up that mountain,' Mick said.

  'It was a bit ambitious,' Andrea agreed. 'It would have been hard enough without the nervelink, given how flabby the two of us have become.'

  'I think I'd have made a better job of it yesterday. Even this morning . . . I honestly felt I could do this when we got into the car.'

  Andrea touched his thigh. 'How does it feel?'

  'Like I'm moving away. Yesterday I felt like I was in this body, fully a part of it. Like a face filling a mask. Today it's different. I can still see through the mask, but it's getting further away.'

  Andrea seemed distant for several moments. He wondered if what he'd said had upset her. But when she spoke again there was something in her voice - a kind of steely resolution - that he hadn't been expecting, but which was entirely Andrea.

  'Listen to me, Mick.'

  'I'm listening.'

  'I'm going to tell you something. It's the first of May today; just past two in the afternoon. We left Cardiff at eleven. This time next year, this exact day, I'm coming back here. I'm going to pack a picnic basket and go all the way up to the top of Pen y Fan. I'll set off from Cardiff at the same time. And I'm going to do it the year after, as well. Every first of May. No matter what day of the week it is. No matter how bloody horrible the weather is. I'm going up this mountain and nothing on Earth is going to stop me.'

  It took him a few seconds to realise what she was getting at. 'With the other Mick?'

  'No. I'm not saying we won't ever climb that hill together. But when I go up it on the first of May, I'll be on my own.' She looked levelly at Mick. 'And you'll do it alone as well. You'll find someone new, I'm sure of it. But whoever she is will have to give you that one day to yourself. So that you and I can have it to ourselves.'

  'We won't be able to communicate. We won't even know the other one's stuck to the plan.'

  'Yes,' Andrea said firmly. 'We will. Because it's going to be a promise, all right? The most important one either of us has ever made in our whole lives. That way we'll know. Each of us will be in our own universe, or worldline, or whatever you call it. But we'll both be standing on the same Welsh mountain. We'll both be looking at the same view. And I'll be thinking of you, and you'll be thinking of me.'

  Mick ran a stiff hand through Andrea's hair. He couldn't get his fingers to work very well now.

  'You really mean that, don't you?'

  'Of course I mean it. But I'm not promising anything unless you agree to your half of it. Would you promise, Mick?'

  'Yes,' he said. 'I will.'

  'I wish I could think of something better. I could say we'd always meet in the park. But there'll be people around; it won't feel private. I want the silence, the isolation, so I can feel your presence. And one day they might tear down the park and put a shopping centre there instead. But the mountain will always be there. At least as long as we're around.'

  'And when we get old? Shouldn't we agree to stop climbing the mountain, when we get to a certain age?'

  'There you go again,' Andrea said. 'Decide for yourself. I'm going to keep climbing this thing until they put me in a box. I expect nothing less from you, Mick Leighton.'

  He made the best smile he was capable of. 'Then . . . I'll just have to do my best, won't I?'

  FRIDAY

  In the morning Mick was paraplegic. The nervelink still worked perfectly, but the rate of data transmission from one worldline to the other had become too low to permit anything as complex and feedback-dependent as walking. His control over the body's fingers had become so clumsy that his hands might as well have been wearing boxing gloves. He could hold something if it was presented to him, but it was becoming increasingly difficult to manipulate simple objects, even those that had presented no difficulty twenty-four hours earlier. When he tried to grasp the breakfast yoghurt, he succeeded only in tipping it over the table. His hand had seemed to lurch towards the yoghurt, crossing the distance too quickly. According to Joe he had lost depth perception overnight. The glasses, sensing the dwindling data rate, were no longer sending stereoscopic images back to the lab.

  He could still move around. The team had anticipated this stage and made sure an electric wheelchair was ready for him. Its chunky controls were designed to be used by someone with only limited upper body coordination. The chair was equipped with a panic button, so that Mick could summon help if he felt his control slipping faster than the predicted rate. Were he to fall into sudden and total paralysis, the chair would call out to passers-by to provide assistance. In the event of an extreme medical emergency, it would steer itself to the nearest designated care point.

  Andrea came out to the laboratory to meet him. Mick wanted one last trip into the city with her, but although she'd been enthusiastic when they'd talked about the plan on the phone, Andrea was now reluctant.

  'Are you sure about this? We had such a nice time on Thursday. It would be a shame to spoil the memory of that now.'

  'I'm okay,' Mick said.

  'I'm just saying, we could always just stroll around the gardens here.'

  'Please,' Mick said. 'This is what . . . I want.'

  His voice was slow, his phrasing imprecise. He sounded drunk and depressed. If Andrea noticed - and he was sure she must have - she made no observation.

  They went into town. It was difficult getting the wheelchair on the tram, even with Andrea's assistance. No one seemed to know how to lower the boarding ramp. One of the benefits of nervelink technology was that you didn't see that many people in wheelchairs any more. The technology that enabled one person to control another person's body also enabled spinal injuries to be bypassed. Mick was aware that he was attracting more attention than on any previous day. For most people wheelchairs were a medical horror from the past, like iron lungs or leg braces.

  On the tram's video monitor he watched a news item about the Polish miners. It wasn't good. The rescue team had had a number of options available to them, involving at least three possible routes to the trapped men. After carefully evaluating all the data - aware of how little time remained for the victims - they'd chosen what had promised to be the quickest and safest approach.

  It had turned out to be a mistake, one that would prove fatal for the miners. The rescuers had hit a flooded section and had been forced to retreat
, with damage to their equipment, and one of their team injured. Yet the miners had been saved in one of the other contacted worldlines. In that reality, one of the members of the rescue team had slipped on ice and fractured his hip while boarding the plane. The loss of that one man - who'd been a vocal proponent for taking the quickest route - had resulted in the team following the second course. It had turned out to be the right decision. They'd met their share of obstacles and difficulties, but in the end they'd broken through to the trapped miners.

  By the time this happened, contact with that worldline had almost been lost. Even the best compression methods couldn't cope with moving images. The pictures that came back, of the men being liberated from the ground, were grainy and monochrome, like a blow-up of newsprint from a hundred years earlier. They'd been squeezed across the gap in the last minutes before noise drowned the signal.

  But the information was useless. Even armed with the knowledge that there was a safe route through to the miners, the team in this worldline didn't have time to act.

  The news didn't help Mick's mood. Going into the city turned out to be exactly the bad move Andrea had predicted. By midday his motor control had deteriorated even further, to the point where he was having difficulty steering the wheelchair. His speech became increasingly slurred, so that Andrea had to keep asking him to repeat himself. In defence, he shut down into monosyllables. Even his hearing was beginning to fail, as the auditory data was compressed to an even more savage degree. He couldn't distinguish birds from traffic, or traffic from the swish of the trees in the park. When Andrea spoke to him she sounded like her words had been fed through a synthesiser, then chopped up and spliced back together in some tinny approximation of her normal voice.

  At three, his glasses could no longer support full colour vision. The software switched to a limited colour palette. The city looked like a hand-tinted photograph, washed out and faded. Andrea's face oscillated between white and sickly grey.

  By four, Mick was fully quadriplegic. By five, the glasses had reverted back to black and white. The frame rate was down to ten images per second, and falling.

  By early evening, Andrea was no longer able to understand what Mick was saying. Mick realised that he could no longer reach the panic button. He became agitated, thrashing his head around. He'd had enough. He wanted to be pulled out of the nervelink, slammed back into his own waiting body. He no longer felt as if he was in Mick's body, but he didn't feel as if he was in his own either. He was strung out somewhere between them, helpless and almost blind. When the panic hit, it was like a foaming, irresistible tide.

  Alarmed, Andrea wheeled him back to the laboratory. By the time she was ready to say goodbye to him, the glasses had reduced his vision to five images per second, each of which was composed of only six thousand pixels. He was calmer then, resigned to the inevitability of what tomorrow would bring: he would not even recognise Andrea in the morning.

  SATURDAY

  Mick's last day with Andrea began in a world of sound and vision - senses that were already impoverished to a large degree - and ended in a realm of silence and darkness.

  He was now completely paralysed, unable even to move his head. The brain that belonged to the other, comatose Mick now had more control over this body than its wakeful counterpart. The nervelink was still sending signals back to the lab, but the requirements of sight and sound now consumed almost all available bandwidth. In the morning, vision was down to one thousand pixels, updated three frames per second. His sight had already turned monochrome, but even yesterday there had been welcome gradations of grey, enough to anchor him into the visual landscape.

  Now the pixels were only capable of registering on or off; it cost too much bandwidth to send intermediate intensity values. When Andrea was near him, her face was a flickering abstraction of black and white squares, like a trick picture in a psychology textbook. With effort he learned to distinguish her from the other faces in the laboratory, but no sooner had he gained confidence in his ability than the quality of vision deteriorated even further.

  By midmorning the frame rate had dropped to eight hundred pixels at two images per second, which was less like vision than being shown a sequence of still pictures. People didn't walk to him across the lab - they jumped from spot to spot, captured in frozen postures. It was soon easy to stop thinking of them as people at all, but simply as abstract structures in the data.

  By noon he could not exactly say that he had any vision at all. Something was updating once every two seconds, but the matrix of black and white pixels was hard to reconcile with his memories of the lab. He could no longer distinguish people from furniture, unless people moved between frames, and then only occasionally. At two, he asked Joe to disable the feed from the glasses, so that the remaining bandwidth could be used for sound and touch. Mick was plunged into darkness.

  Sound had declined overnight as well. If Andrea's voice had been tinny yesterday, today it was barely human. It was as if she were speaking to him through a voice distorter on the end of the worst telephone connection in the world. The noise was beginning to win. The software was struggling to compensate, teasing sense out of the data. It was a battle that could only be prolonged, not won.

  'I'm still here,' Andrea told him, her voice a whisper fainter than the signal from the furthest quasar.

  Mick answered her. It took some time. His words in the lab had to be analysed by voice-recognition software and converted into ASCII characters. The characters were compressed further and sent across the reality gap, bit by bit. In the other version of the lab - the one where Mick's body waited in a wheelchair, the one where Andrea hadn't died in a car crash - equivalent software decompressed the character string and reconstituted it in mechanically generated speech, with an American accent.

  'Thank you for letting me come back,' he said. 'Please stay. Until the end. Until I'm not here any more.'

  'I'm not going anywhere, Mick.'

  Andrea squeezed his hand. After all that he had lost since Friday, touch remained. It really was the easiest thing to send: easier than sight, easier than sound. When, later, even Andrea's voice had to be sent across the gap by character string and speech synthesiser, touch endured. He felt her holding him, hugging his body to hers, refusing to surrender him to the drowning roar of quantum noise.

  'We're down to less than a thousand useable bits,' Joe told him, speaking quietly in his ear in the version of the lab where Mick lay on the immersion couch. 'That's a thousand bits total, until we lose all contact. It's enough for a message, enough for parting words.'

  'Send this,' Mick said. 'Tell Andrea that I'm glad she was there. Tell her that I'm glad she was my wife. Tell her I'm sorry we didn't make it up that hill together.'

  When Joe had sent the message, typing it in with his usual fluid speed, Mick felt the sense of Andrea's touch easing. Even the microscopic data-transfer burden of communicating unchanging pressure, hand on hand, body against body, was now too much for the link. It was like one swimmer letting a drowning partner go. As the last bits fell, he felt Andrea slip away for ever.

  He lay on the couch, unmoving. He had lost his wife, for the second time. For the moment the weight of that realisation pinned him into stillness. He did not think he would ever be able to walk in his world, let alone the one he had just vacated.

  And yet it was Saturday. Andrea's funeral was in two days. He would have to be ready for that.

  'We're done,' Joe said respectfully. 'Link is now noise-swamped.'

  'Did Andrea send anything back?' Mick asked. 'After I sent my last words--'

  'No. I'm sorry.'

  Mick caught the hesitation in Joe's answer. 'Nothing came through?'

  'Nothing intelligible. I thought something was coming through, but it was just . . .' Joe offered an apologetic shrug. 'The set-up at their end must have gone noise-limited a few seconds before ours did. Happens, sometimes.'

  'I know,' Mick said. 'But I still want to see what Andrea sent.'

 
Joe handed him a printout. Mick waited for his eyes to focus on the sheet. Beneath the lines of header information was a single line of text: SO0122215. Like a phone number or a postal code, except it was obviously neither.

  'That's all?'

  Joe sighed heavily. 'I'm sorry, mate. Maybe she was just trying to get something through . . . but the noise won. The fucking noise always wins.'

  Mick looked at the numbers again. They began to talk to him. He thought he knew what they meant.

  'Always fucking wins,' Joe repeated.

  SUNDAY

  Andrea was there when they brought Mick out of the medically induced coma. He came up through layers of disorientation and half-dream, adrift until something inside him clicked into place and he realised where he had been for the last week, what had been happening to the body over which he was now regaining gradual control. It was exactly as they had promised: no dreams, no anxiety, no tangible sense of elapsed time. In a way, it was not an entirely unattractive way to spend a week. Like being in the womb, he'd heard people say. And now he was being born again, a process that was not without its own discomforts. He tried moving an arm and when the limb did not obey him instantly, he began to panic. But Joe was already smiling.