Treena had stopped in front of me.

We were about to move when Mum stepped forward.

In other circumstances I suppose it might have seemed strange that I, Lou Clark, a girl who had rarely been more than a bus ride from her home town in twenty years, was now flying to her third country in less than a week. But I packed an overnight case with the swift efficiency of an air stewardess, rejecting all but the barest necessities. Treena ran around silently fetching any other things she thought I might need, and then we headed downstairs. We stopped halfway down. Mum and Dad were already in the hall, standing side by side in the ominous way they used to do when we sneaked back late from a night out.

"What's going on?" Mum was staring at my case.

"Lou's going to Switzerland," she said. "And she needs to leave now. There's only one flight left today."

"No." Her mouth was set into an unfamiliar line, her arms folded awkwardly in front of her. "Really. I don't want you involved. If this is what I think it is, then no."

"Your mum's right," Dad said.

"No," said Mum, and her voice held an unusually steely quality. "No buts. I've been thinking about this, about everything you told us. It's wrong. Morally wrong. And if you get embroiled in it and you're seen to be helping a man kill himself, then you could end up in all sorts of trouble."

"But --" Treena began, glancing behind at me.

"He's asked for her to come. She can't just ignore him," Treena interrupted.

"We've seen it in the news. This could affect your whole life, Lou. This college interview, everything. If you get a criminal record, you will never get a college degree or a good job or anything --"

"Yes. Yes, she can. She's given six months of her life to this family. And a fat lot of good it's brought her, judging by the state of things. A fat lot of good it's brought this family, with people banging on the door and all the neighbours thinking we've been done for benefit fraud or some such. No, she's finally got the chance to make something of herself, and now they want her to go to that dreadful place in Switzerland and get involved in God knows what. Well, I say no. No, Louisa."

"Granddad is different."

"No, she doesn't. She's done enough. She said herself last night, she's done everything she could." Mum shook her head. "Whatever mess the Traynors are going to make of their lives going to this… this… whatever they're going to do to their own son, I don't want Louisa involved. I don't want her ruining her whole life."

"But she has to go," Treena said.

"It's not my decision, Mum. It's Will's. The whole point of this is to support Will."

"I think I can make my own mind up," I said.

"I'm not sure you can. This is your friend, Louisa. This is a young man with his whole life ahead of him. You cannot be part of this. I'm… I'm shocked that you could even consider it." Mum's voice had a new, hard edge. "I didn't bring you up to help someone end his life! Would you end Granddad's life? Do you think we should shove him off to Dignitas too?"

"No, he isn't. He can't do what he used to. But his life is precious. Just as Will's is precious."

"Support Will? I've never heard such rubbish. You are a child, Louisa. You've seen nothing, done nothing. And you have no idea what this is going to do to you. How in God's name will you ever be able to sleep at night if you help him to go through with it? You'd be helping a man to die. Do you really understand that? You'd be helping Will, that lovely, clever young man, to die."

The little hallway grew silent. Mum stared at me like she had no idea who I was. I took a step closer to her, trying to make her understand. But as I did, she took a step back.

"I'd sleep at night because I trust Will to know what is right for him, and because what has been the worst thing for him has been losing the ability to make a single decision, to do a single thing for himself…" I looked at my parents, trying to make them understand. "I'm not a child. I love him. I love him, and I shouldn't have left him alone, and I can't bear not being there and not knowing what… what he's…" I swallowed. "So yes. I'm going. I don't need you to look out for me or understand. I'll deal with it. But I'm going to Switzerland -- whatever either of you says."

"Mum? I owe Will. I owe it to him to go. Who do you think got me to apply to college? Who do you think encouraged me to make something of myself, to travel places, to have ambitions? Who changed the way I think about everything? About myself even? Will did. I've done more, lived more, in the last six months than in the last twenty-seven years of my life. So if he wants me to go to Switzerland, then yes, I'm going to go. Whatever the outcome."

But Mum broke the silence. "If you go, Louisa, you needn't come back."

There was a brief silence."She's like Aunt Lily," Dad said, quietly.

We all stood, staring at each other. Dad and Treena were shooting glances at each other, as if each of them were waiting for the other to say something.

The words fell out of her mouth like pebbles. I looked at my mother in shock. Her gaze was unyielding. It tensed as she watched for my reaction. It was as if a wall I had never known was there had sprung up between us.

"Mum?"

"Josie…"

"I mean it. This is no better than murder."

"That's the truth, Bernard. I can't be part of this."

I remember thinking, as if at a distance, that I had never seen Katrina look so uncertain as she did now. I saw Dad's hand reach out to Mum's arm, whether in reproach or comfort I couldn't tell. My mind went briefly blank. Then almost without knowing what I was doing, I walked slowly down the stairs and past my parents to the front door. And after a second, my sister followed me.

The corners of Dad's mouth turned down, as if he were struggling to contain all sorts of things. Then he turned to Mum, and placed one hand on her shoulder. Her eyes searched his face and it was as if she already knew what he was going to say.

"Here," he said. "Go out the back door, through Mrs Doherty's garden, and take the van. They won't see you in the van. If you go now and the traffic's not too bad you might just make it."

She glanced sideways at me as we sped down the motorway.

"You have any idea where this is all headed?" Katrina said.

I couldn't look at her for long -- I was rifling through my handbag, trying to work out what I had forgotten. I kept hearing the sound of Mrs Traynor's voice down the line. Louisa? Please will you come? I know we've had our differences, but please… It's vital that you come now.

"Nope."

And then he threw Treena his keys. She caught them one-handed.

"Shit. I've never seen Mum like that," Treena continued.

Katrina glanced sideways at me. "I mean, she's mad now, but she's in shock. You know she'll be all right in the end, right? I mean, when I came home and told her I was up the duff I thought she was never going to speak to me again. But it only took her -- what? -- two days, to come round."

Passport, wallet, door keys. Door keys? For what? I no longer had a home.

"Treen?"

"Yes?"

I could hear her babbling away beside me, but I wasn't really paying attention. I could barely focus on anything. My nerve endings seemed to have come alive; they almost jangled with anticipation. I was going to see Will. Whatever else, I had that. I could almost feel the miles between us shrinking, as if we were at two ends of some invisible elastic thread.

"Hey! Lou!"

I swallowed. "Don't let me miss this flight."

"Sorry." I turned back and ran the few steps to her.

My sister is nothing if not determined. We queue-jumped, sped up the inside lane, broke the speed limit and scanned the radio for the traffic reports, and finally the airport came into view. She screeched to a halt and I was halfway out of the car before I heard her.

She hugged me, really tightly. "You're doing the right thing," she said. She looked almost close to tears. "Now fuck off. If you miss the bloody plane on top of me getting six points on my licence, I'm never talking to you again."

I didn't look back. I ran all the way to the Swiss Air desk and it took me three goes to say my name clearly enough to request my tickets.

I stared groggily around the unfamiliar room, at the heavy burgundy drapes, designed to block out light, at the large flat-screen television, at my overnight bag, which I hadn't even bothered to unpack. I checked the clock, which said it was shortly after seven Swiss time. And as I realized where I was, I suddenly felt my stomach clench with fear.

I arrived in Zurich shortly before midnight. Given the late hour, Mrs Traynor had, as promised, booked me into a hotel at the airport and said she would send a car for me at nine the following morning. I had thought I wouldn't sleep, but I did -- an odd, heavy and disjointed trawl through the hours -- waking up at seven the next morning with no idea where I was.

I scrambled out of bed just in time to be sick in the little bathroom. I sank down on the tiled floor, my hair sticking to my forehead, my cheek pressed against the cold porcelain. I heard my mother's voice, her protests, and I felt a dark fear creeping over me. I wasn't up to this. I didn't want to fail again. I didn't want to have to watch Will die. With an audible groan, I scrambled up to be sick again.

I couldn't eat. I managed to swallow down a cup of black coffee and showered and dressed, and that took me to 8am. I stared at the pale-green dress I had thrown in last night and wondered if it was appropriate for where I was going. Would everyone wear black? Should I have worn something more vibrant and alive, like the red dress I knew Will liked? Why had Mrs Traynor called me here? I checked my mobile phone, wondering whether I could call Katrina. It would be seven in the morning there now. But she would probably be dressing Thomas, and the thought of talking to Mum was too much. I put on some make-up and then sat down by the window, and the minutes ticked slowly past.

When I couldn't bear being in the little room any longer, I threw the last of my things into my bag and left. I would buy a newspaper, and wait in the lobby. It couldn't be worse than sitting in my room with the silence or the satellite news channel and the suffocating darkness of the curtains. It was as I was passing reception that I saw the computer terminal, discreetly placed in a corner. It was marked: For Use Of Guests. Please Ask At Reception.

I don't think I had ever felt lonelier in my life.

Ritchie. Are you there?

What do I say to him? How do I change his mind?

Because I can't not be here. He asked me. Am in hotel waiting to go see him.

Then why are you there?

I hesitated, then typed:

He knew what it meant. They all knew what it meant. The clinic had been the subject of many heated debates. I typed:

If he's in Switzerland, Bee, I'm not sure he's going to change his mind.

I'm frightened.

I have no idea how this day is going to end.

I am about to begin the strangest day of my life. I am in Switzerland.

She nodded, and I bought an hour's token. I knew suddenly very clearly who I wanted to speak to. I knew in my gut that he was one of the few people I could rely on to be online at this time. I logged on to the chat room and typed on the message board:

I hesitated for just a moment before typing:

Oh, Bee.

"Can I use this?" I said to the receptionist.

Morning, Bee. You're early today?

There was a delay before he typed again. His words appeared on the screen more slowly than usual, as if he were taking great care.

It's not my choice. It's not the choice of most of us on this board. I love my life, even if I wish it was different. But I understand why your friend might well have had enough. It's tiring, leading this life, tiring in a way the AB can never truly understand. If he is determined, if he really can't see a way of things being better for him, then I guess the best thing you can do is just be there. You don't have to think he's right. But you do have to be there.

I will.

I realized I was holding my breath.

Good luck, Bee. And come see me after. Things may get a little bumpy for you afterwards. Either way, I could do with a friend like you.

I felt a huge lump in my throat, and swallowed it. Ritchie was still typing.

My fingers stilled on the keyboard. I typed:

And then the receptionist told me that my car had arrived outside.

I don't know what I expected -- maybe some white building next to a lake, or snow-capped mountains. Perhaps some medical-looking marble frontage with a gold-plated plaque on the wall. What I didn't expect was to be driven through an industrial estate until I arrived at what looked remarkably like an ordinary house, surrounded by factories and, weirdly, a football pitch. I walked across decking, past a goldfish pond, and then I was in.

The woman who opened the door knew immediately who I was looking for. "He is here. Would you like me to show you?"

I stalled then. I stared at the closed door, oddly similar to the one I had stood outside in Will's annexe all those months ago, and I took a breath. And nodded.

I saw the bed before I saw him; it dominated the room with its mahogany wood, its quaintly flowered quilt and pillows weirdly out of place in that setting. Mr Traynor sat on one side of it, Mrs Traynor on the other.

The room itself was light and airy, like an upmarket holiday home. There was a tiled floor and expensive rugs, and a sofa at the end that looked out on to a little garden. I didn't know what to say. It was such a ridiculous, mundane sight, the three of them sitting there, as if they were a family trying to work out where to go sightseeing that day.

Georgina was seated on a wooden chair in the corner, bent over her knees, her hands pressed together as if in prayer. She lifted her gaze as I walked in, revealing shadowed eyes, reddened with grief, and I felt a brief spasm of sympathy for her.

She looked ghostly pale, and stood up when she saw me. "Louisa."

What would I have done if Katrina had insisted on her right to do the same?

Will's eyes locked on to mine and despite everything, despite all my fears, the fact that I had thrown up twice, that I felt like I hadn't slept for a year, I was suddenly glad I had come. Not glad, relieved. Like I had excised some painful, nagging part of myself, and given it over.

I turned towards the bed. "So," I said, my bag over my shoulder, "I'm guessing the room service isn't up to much?"

Weirdly, I found myself smiling back. "Nice room," I said, and immediately realized the idiocy of the remark. I saw Georgina Traynor close her eyes, and I blushed.

And then he smiled. It was lovely, his smile -- a slow thing, full of recognition.

"Of course."

She tried to smile. I saw a million things in the way she looked at me then -- relief, gratitude, a faint resentment at being shut out of these few minutes, perhaps even a distant hope that my appearance meant something, that this fate might yet be twisted from its tracks.

Will turned towards his mother. "I want to talk to Lou. Is that okay?"

She moved past me into the corridor, and as I stood back from the doorway to let her pass, she reached out a hand and touched my upper arm, just lightly. Our eyes met, and hers softened, so that briefly she looked like someone else entirely, and then she turned away from me.

"So…"

And there it was. He knew it, and I knew it. There was nothing left for me to do.

"If you're here, you accept it's my choice. This is the first thing I've been in control of since the accident."

Do you know how hard it is to say nothing? When every atom of you strains to do the opposite? I had practised not saying anything the whole way from the airport, and it was still nearly killing me. I nodded. When I finally spoke, my voice was a small, broken thing. What emerged was the only thing I could safely say.

"You're not going to --"

Georgina stood slowly and walked out silently, her very back broadcasting her reluctance.

"I'm not going to try and change your mind."

And then it was just us.

Will was half propped up in the bed, able to see out of the window to his left, where the water feature in the little garden merrily trickled a thin stream of clear water below the decking. On the wall was a badly framed print picture of dahlias. I remember thinking that was a really crummy print to have to look at in your last hours.

"Come, Georgina," she said, when her daughter made no attempt to move.

"I know."

He seemed to relax then. "Come over here." And then, when I hesitated. "Please. Come on. Right here, on the bed. Right next to me."

"I missed you."

I realized then that there was actual relief in his expression. That he was pleased to see me in a way he wasn't actually going to be able to say. And I told myself that it was going to have to be enough. I would do the thing he had asked for. That would have to be enough.

I lay down on the bed beside him and I placed my arm across him. I rested my head on his chest, letting my body absorb the gentle rise and fall of it. I could feel the faint pressure of Will's fingertips on my back, his warm breath in my hair. I closed my eyes, breathing in the scent of him, still the same expensive cedar-wood smell, despite the bland freshness of the room, the slightly disturbing scent of disinfectant underneath. I tried not to think of anything at all. I just tried to be, tried to absorb the man I loved through osmosis, tried to imprint what I had left of him on myself. I did not speak. And then I heard his voice. I was so close to him that when he spoke it seemed to vibrate gently through me.

"Hey, Clark," he said. "Tell me something good."

I stared out of the window at the bright-blue Swiss sky and I told him a story of two people. Two people who shouldn't have met, and who didn't like each other much when they did, but who found they were the only two people in the world who could possibly have understood each other. And I told him of the adventures they had, the places they had gone, and the things I had seen that I had never expected to. I conjured for him electric skies and iridescent seas and evenings full of laughter and silly jokes. I drew a world for him, a world far from a Swiss industrial estate, a world in which he was still somehow the person he had wanted to be. I drew the world he had created for me, full of wonder and possibility. I let him know a hurt had been mended in a way that he couldn't have known, and for that alone there would always be a piece of me indebted to him. And as I spoke I knew these would be the most important words I would ever say and that it was important that they were the right words, that they were not propaganda, an attempt to change his mind, but respectful of what Will had said.

There was a long silence.

"You're angry. Please. I don't want to hurt you or make you --"

"Look at me. Please."

"It has been," I told him, "the best six months of my entire life."

I screwed my eyes shut and shook my head.

And then, just like that, my heart broke. My face crumpled, my composure went and I held him tightly and I stopped caring that he could feel the shudder of my sobbing body because grief swamped me. It overwhelmed me and tore at my heart and my stomach and my head and it pulled me under, and I couldn't bear it. I honestly thought I couldn't bear it.

"Don't, Clark," he murmured. I felt his lips on my hair. "Oh, please. Don't. Look at me."

"Funnily enough, Clark, mine too."

Time slowed, and stilled. It was just the two of us, me murmuring in the empty, sunlit room. Will didn't say much. He didn't answer back, or add a dry comment, or scoff. He nodded occasionally, his head pressed against mine, and murmured, or let out a small sound that could have been satisfaction at another good memory.

I couldn't.

I told him something good.

It took some time to regain my composure. I blew my nose, took a long deep breath. Finally, I raised myself on my elbow, and I looked back at him. His eyes, so long strained and unhappy, looked oddly clear and relaxed.

"Funny."

"No…" I shook my head again. "It's not that. I don't want…" My cheek was pressed to his chest. "I don't want the last thing you see to be my miserable, blotchy face."

"You still don't get it, Clark, do you?" I could hear the smile in his voice. "It's not your choice."

"You look absolutely beautiful."

"Come here," he said. "Right up close to me."

I lay down again, facing him. I saw the clock above the door and had a sudden sense of time running out. I took his arm and wrapped it tightly around me, threading my own arms and legs around him so that we were tightly entwined. I took his hand -- the good one -- and wrapped my fingers in his, kissing the knuckles as I felt him squeeze mine. His body was so familiar to me now. I knew it in a way I had never known Patrick's -- its strengths and vulnerabilities, its scars and scents. I placed my face so close to his that his features became indistinct, and I began to lose myself in them. I stroked his hair, his skin, his brow, with my fingertips, tears sliding unchecked down my cheeks, my nose against his, and all the time he watched me silently, studying me intently as if he were storing each molecule of me away. He was already retreating, withdrawing to somewhere I couldn't reach him.

I realized I was afraid of living without him. How is it you have the right to destroy my life, I wanted to demand of him, but I'm not allowed a say in yours?

I kissed him, trying to bring him back. I kissed him and let my lips rest against his so that our breath mingled and the tears from my eyes became salt on his skin, and I told myself that, somewhere, tiny particles of him would become tiny particles of me, ingested, swallowed, alive, perpetual. I wanted to press every bit of me against him. I wanted to will something into him. I wanted to give him every bit of life I felt and force him to live.

I blinked at him.

So I held him, Will Traynor, ex-City whiz kid, ex-stunt diver, sportsman, traveller, lover. I held him close and said nothing, all the while telling him silently that he was loved. Oh, but he was loved.

He gave me a small smile, almost an apology.

But I had promised.

I couldn't say how long we stayed like that. I was dimly aware of soft conversation outside, of the shuffle of shoes, a distant church bell ringing in some far-off place. Finally, I felt him loosen a great breath, almost a shudder, and he drew his head back just an inch so that we could see each other clearly.

"Clark," he said, quietly. "Can you call my parents in?"