I watched the news reports and listened to the legal arguments from pro-lifers and esteemed moral philosophers, and didn't quite know where I stood on any of it. It all seemed weirdly unrelated to Will.

We, in the meantime, had gradually been increasing Will's outings -- and the distance that he was prepared to travel. We had been to the theatre, down the road to see the morris dancers (Will kept a straight face at their bells and hankies, but he had gone slightly pink with the effort), driven one evening to an open-air concert at a nearby stately home (more his thing than mine), and once to the multiplex where, due to inadequate research on my part, we ended up watching a film about a girl with a terminal illness.

May was a strange month. The newspapers and television were full of headlines about what they termed "the right to die". A woman suffering from a degenerative disease had asked that the law be clarified to protect her husband, should he accompany her to Dignitas when her suffering became too much. A young football player had committed suicide after persuading his parents to take him there. The police were involved. There was to be a debate in the House of Lords.

The football player's parents had been savaged by the tabloid newspapers. How Could They Let Him Die? screamed the headlines. I couldn't help but feel the same way. Leo McInerney was twenty-four. He had lived with his injury for almost three years, so not much longer than Will. Surely he was too young to decide that there was nothing left to live for? And then I read what Will had read -- not an opinion piece, but a carefully researched feature about what had actually taken place in this young man's life. The writer seemed to have had access to his parents.

But I knew he saw the headlines too. He had begun using the computer more since we got the new software, and he had worked out how to move a mouse by dragging his thumb across a trackpad. This laborious exercise enabled him to read the day's newspapers online. I brought him in a cup of tea one morning to find him reading about the young football player -- a detailed feature about the steps he had gone through to bring about his own death. He blanked the screen when he realized I was behind him. That small action left me with a lump somewhere high in my chest that took a full half-hour to go away.

I looked up the same piece at the library. I had begun to read newspapers. I had worked out which of their arguments tended to go deeper -- that information wasn't always at its most useful boiled down to stark, skeletal facts.

He had tried to commit suicide twice by starving himself until hospitalized, and when returned home had begged his parents to smother him in his sleep. When I read that, I sat in the library and stuck the balls of my hands in my eyes until I could breathe without sobbing.

Leo, they said, had played football since he was three years old. His whole life was football. He had been injured in what they termed a "million to one" accident when a tackle went wrong. They had tried everything to encourage him, to give him a sense that his life would still hold value. But he had retreated into depression. He was an athlete not just without athleticism, but without even the ability to move or, on occasion, breathe without assistance. He gleaned no pleasure from anything. His life was painful, disrupted by infection, and dependent on the constant ministrations of others. He missed his friends, but refused to see them. He told his girlfriend he wouldn't see her. He told his parents daily that he didn't want to live. He told them that watching other people live even half the life he had planned for himself was unbearable, a kind of torture.

Dad lost his job. He was pretty brave about it. He came home that afternoon, got changed into a shirt and tie and headed back into town on the next bus, to register at the Job Centre.

But if I had found it hard to get employment, prospects for a 55-year-old man who had only ever held one job were harder. He couldn't even get a job as a warehouseman or a security guard, he said, despairingly, as he returned home from another round of interviews. They would take some unreliable snot-nosed seventeen-year-old because the government would make up their wages, but they wouldn't take a mature man with a proven work record. After a fortnight of rejections, he and Mum admitted they would have to apply for benefits, just to tide them over, and spent their evenings poring over incomprehensible, fifty-page forms which asked how many people used their washing machine, and when was the last time they had left the country (Dad thought it might have been 1988). I put Will's birthday money into the cash tin in the kitchen cupboard. I thought it might make them feel better to know they had a little security.

He had already decided, he told Mum, that he would apply for anything, despite being a skilled craftsman with years of experience. "I don't think we can afford to be picky at the moment," he said, ignoring Mum's protestations.

When I woke up in the morning, it had been pushed back under my door in an envelope.

On the Friday after my dad lost his job, Will received an invitation -- a wedding invitation from Alicia and Rupert. Well, strictly speaking, the invitation came from Colonel and Mrs Timothy Dewar, Alicia's parents, inviting Will to celebrate their daughter's marriage to Rupert Freshwell. It arrived in a heavy parchment envelope with a schedule of celebrations, and a fat, folded list of things that people could buy them from stores I had never even heard of.

The tourists came, and the town began to fill. Mr Traynor was around less and less now; his hours lengthened as the visitor numbers to the castle grew. I saw him in town one Thursday afternoon, when I walked home via the dry cleaner's That wouldn't have been unusual in itself, except for the fact he had his arm around a red-haired woman who clearly wasn't Mrs Traynor. When he saw me he dropped her like a hot potato.

I turned away, pretending to peer into a shop window, unsure if I wanted him to know that I had seen them, and tried very hard not to think about it again.

"She's got some nerve," I observed, studying the gilt lettering, the gold-edged piece of thick card. "Want me to throw it?"

Will gave me another book of short stories, one that he'd ordered from Amazon, and a copy of The Red Queen. I knew it wasn't going to be my sort of book at all. "It hasn't even got a story," I said, after studying the back cover.

"Whatever you want." Will's whole body was a study in determined indifference.

Perhaps it was something to do with the speed with which he turned away and began busying himself with his computer keyboard. Perhaps it was his tone of voice. But for some reason I didn't throw it away. I put it carefully into his folder in the kitchen.

I stared at the list. "What the hell is a couscoussier anyway?"

"So?" Will replied. "Challenge yourself a bit."

I tried -- not because I really had an appetite for genetics -- but because I couldn't bear the thought that Will would go on and on at me if I didn't He was like that now. He was actually a bit of a bully. And, really annoyingly, he would quiz me on how much I had read of something, just to make sure I really had.

"Thank God," he would reply, with feeling.

Will looked up from his computer screen. "Oh yes?"

"You're not my teacher," I would grumble.

"What if the genetically superior male is actually a bit of a dickhead?"

This book -- which was actually surprisingly readable -- was all about a kind of battle for survival. It claimed that women didn't pick men because they loved them at all. It said that the female of the species would always go for the strongest male, in order to give her offspring the best chance. She couldn't help herself. It was just the way nature was.

On the third Saturday of May, Treena and Thomas came home. My mother was out of the door and up the garden path before they had made it halfway down the street. Thomas, she swore, clutching him to her, had grown several inches in the time they had been away. He had changed, was so grown-up, looked so much the little man. Treena had cut off her hair and looked oddly sophisticated. She was wearing a jacket I hadn't seen before, and strappy sandals. I found myself wondering, meanly, where she had found the money.

He had been going on and on about this for the best part of an afternoon when I butted in. "There's one thing this Matt Ridley bloke hasn't factored in," I said.

I didn't agree with this. And I didn't like the argument. There was an uncomfortable undercurrent to what he was trying to persuade me of. Will was physically weak, damaged, in this author's eyes. That made him a biological irrelevance. It would have made his life worthless.

"Great. Really good. I mean, it's hard not having any help with Thomas, and it did take him a while to settle in at the crèche." She leant forwards. "Although you mustn't tell Mum -- I told her he was fine."

Treena's face broke out into a smile. "It's the best. I can't tell you, Lou, the joy of just using my brain again. I feel like there's been this big chunk of me missing for ages… and it's like I've found it again. Does that sound wanky?"

"But you like the course."

"So how is it?" I asked, while Mum walked Thomas around the garden, showing him the frogs in the tiny pond. Dad was watching football with Granddad, exclaiming in mild frustration at another supposed missed opportunity.

I shook my head. I was actually glad for her. I wanted to tell her about the library, and the computers, and what I had done for Will. But I thought this should probably be her moment. We sat on the foldaway chairs, under the tattered sunshade, and sipped at our mugs of tea. Her fingers, I noticed, were all the right colours.

"She misses you," I said.

"We'll be back most weekends from now on. I just needed… Lou, it wasn't just about settling Thomas in. I just needed a bit of time to be away from it all. I just wanted time to be a different person."

"He's not my disabled bloke. His name's Will."

She looked a bit like a different person. It was weird. Just a few weeks away from home could rub the familiarity right off someone. I felt like she was on the path to being someone I wasn't quite sure of. I felt, weirdly, as if I were being left behind.

"Sorry. Will. So it's going well, then, the old anti-bucket list?"

"Do you think…?" I could see her working out the best way to put it. "Do you think you'll win?"

"So-so. Some trips have been more successful than others." I told her about the horse racing disaster, and the unexpected triumph of the violin concert. I told her about our picnics, and she laughed when I told her about my birthday dinner.

"Mum told me your disabled bloke came to dinner."

Like it was some kind of contest.

She raised an eyebrow.

Mum was cheerful over supper that night. She had cooked lasagne, Treena's favourite, and Thomas was allowed to stay up as a treat. We ate and talked and laughed and talked about safe things, like the football team, and my job, and what Treena's fellow students were like. Mum must have asked Treena a hundred times if she was sure she was managing okay on her own, whether there was anything she needed for Thomas -- as if they had anything spare they could have given her. I was glad I had warned Treena about how broke they were. She said no, gracefully and with conviction. It was only afterwards I thought to ask if it was the truth.

"That's the problem, Treen," I said, and threw the rest of my tea into the flower bed. "People always are."

She looked at me carefully. "Mum says he's really nice."

"No. Really, I did. It was… emotional."

But perhaps my sister was smarter than that. "Anyway. She was definitely surprised. I think she was prepared for Quasimodo."

"A spinal injury doesn't mean you turn into Quasimodo." Please don't say anything about it being a tragic waste, I told her silently.

"I can't believe you went to a violin concert, though. You, of all people!"

"And handsome."

I pulled a tendril from the honeysuckle and began picking off its leaves. "I don't know. I think I'm going to need to up my game." I told her what Mrs Traynor had said to me about going abroad.

"He is really nice."

"I liked it."

At four I woke to the sound of my door creaking open. I blinked groggily, turning towards the light. Thomas stood silhouetted against the doorway, his oversized pyjamas loose around his legs, his comfort blanket half spooled on the floor. I couldn't see his face, but he stood there uncertainly, as if unsure what to do next.

That night I was woken at midnight by the sound of crying. It was Thomas, in the box room. I could hear Treena trying to comfort him, to reassure him, the sound of the light going on and off, a bed being rearranged. I lay in the dark, watching the sodium light filter through my blinds on to my newly painted ceiling, and waited for it to stop. But the same thin wail began again at two. This time, I heard Mum padding across the hallway, and murmured conversation. Then, finally, Thomas was silent again.

"Come here, Thomas," I whispered. As he padded towards me, I could see he was still half asleep. His steps were halting, his thumb thrust into his mouth, his treasured blanket clutched to his side. I held the duvet open and he climbed into bed beside me, his tufty head burrowing into the other pillow, and curled up into a foetal ball. I pulled the duvet over him and lay there, gazing at him, marvelling at the certainty and immediacy of his sleep.

"What was the best place you've ever visited?"

"Night, night, sweetheart," I whispered, and kissed his forehead, and a fat little hand crept out and took a chunk of my T-shirt in its grasp, as if to reassure itself that I couldn't move away.

We were sitting in the shelter, waiting for a sudden squall to stop so that we could walk around the rear gardens of the castle. Will didn't like going to the main area -- too many people to gawp at him. But the vegetable gardens were one of its hidden treasures, visited by few. Its secluded orchards and fruit gardens were separated by honeyed pea-shingle paths that Will's chair could negotiate quite happily.

"Okay. Jesus, that's hot. Give me a minute." He squinted into the distance. "I climbed Mount Kilimanjaro when I hit thirty. That was pretty incredible."

"In terms of what? And what's that?"

I poured some soup from a flask and held it up to his lips. "Tomato."

"How high?"

"A little over nineteen thousand feet to Uhuru Peak. That said, I pretty much crawled the last thousand or so. The altitude hits you pretty hard."

"Trou d"Eau Douce bay, Mauritius. Lovely people, beautiful beaches, great diving. Um… Tsavo National Park, Kenya, all red earth and wild animals. Yosemite. That's California. Rock faces so tall your brain can't quite process the scale of them."

"So where else have you liked?"

"Was it cold?"

Will was silent for a moment. I watched him, wondering where he really was. When we had these conversations he became like the boy in my class, the boy who had distanced himself from us by venturing away.

He told me of a night he'd spent rock climbing, perched on a ledge several hundred feet up, how he'd had to pin himself into his sleeping bag, and attach it to the rock face, because to roll over in his sleep would have been disastrous.

"No…" he smiled at me. "It's not like Everest. Not the time of year that I went, anyway." He gazed off into the distance, briefly lost in his remembrance. "It was beautiful. The roof of Africa, they call it. When you're up there, it's like you can actually see to the end of the world."

"I like more metropolitan places too. Sydney, I loved. The Northern Territories. Iceland. There's a place not far from the airport where you can bathe in the volcanic springs. It's like a strange, nuclear landscape. Oh, and riding across Central China. I went to this place about two days' ride from the Capital of Sichuan province, and the locals spat at me because they hadn't seen a white person before."

He turned to me in surprise.

"You've actually just described my worst nightmare, right there."

He took another sip of soup. "North Korea?" He pondered. "Oh, I've never been to Disneyland. Will that do? Not even Eurodisney."

"I once booked a ticket to Australia. Never went, though."

"Is there anywhere you haven't been?"

"Stuff happened. It's fine. Perhaps I will go one day."

"Not 'perhaps'. You've got to get away from here, Clark. Promise me you won't spend the rest of your life stuck around this bloody parody of a place mat."

"I just… can't bear the thought of you staying around here forever." He swallowed. "You're too bright. Too interesting." He looked away from me. "You only get one life. It's actually your duty to live it as fully as possible."

"Promise me? Why?" I tried to make my voice light. "Where are you going?"

"Le Marais?"

"Right now?"

"Right now. And you're not allowed to say Kilimanjaro. It has to be somewhere I can imagine going myself."

I turned to face him, lowering my voice. "We could go," I said. "We could do it on the Eurostar. It would be easy. I don't think we'd even need to ask Nathan to come. I've never been to Paris. I'd love to go. Really love to go. Especially with someone who knows his way around. What do you say, Will?"

"Okay," I said, carefully. "Then tell me where I should go. Where would you go, if you could go anywhere?"

When Will's face relaxed, he looked like someone quite different. A smile settled across his face now, his eyes creasing with pleasure. "Paris. I would sit outside a cafe in Le Marais and drink coffee and eat a plate of warm croissants with unsalted butter and strawberry jam."

"It's a little district in the centre of Paris. It is full of cobbled streets and teetering apartment blocks and gay men and orthodox Jews and women of a certain age who once looked like Brigitte Bardot. It's the only place to stay."

"No."

"No."

"But you just told me --"

"What?" It took me a moment to drag myself away from that roadside table.

"You don't get it, Clark. I don't want to go there in this -- this thing." He gestured at the chair, his voice dropping. "I want to be in Paris as me, the old me. I want to sit in a chair, leaning back, my favourite clothes on, with pretty French girls who pass by giving me the eye just as they would any other man sitting there. Not looking away hurriedly when they realize I'm a man in an overgrown bloody pram."

"But we could try," I ventured. "It needn't be --"

"No. No, we couldn't Because at the moment I can shut my eyes and know exactly how it feels to be in the Rue des Francs Bourgeois, cigarette in hand, clementine juice in a tall, cold glass in front of me, the smell of someone's steak frites cooking, the sound of a moped in the distance. I know every sensation of it."

I could see myself in that cafe. I was there, at that table, maybe admiring a new pair of French shoes, purchased in a chic little boutique, or picking at a pastry with Parisian red fingernails. I could taste the coffee, smell the smoke from the next table's Gauloises.

It's possible he realized I was a bit subdued, because he leant into me a little. And his face softened. "So, Clark. The rain seems to have stopped. Where shall we go this afternoon. The maze?"

His voice had hardened. I screwed the top back on the vacuum flask. I examined my shoes quite carefully as I did it, because I didn't want him to see my face.

He swallowed. "The day we go and I'm in this bloody contraption, all those memories, those sensations will be wiped out, erased by the struggle to get behind the table, up and down Parisian kerbs, the taxi drivers who refuse to take us, and the wheelchair bloody power pack that wouldn't charge in a French socket. Okay?"

"Okay." Will took a deep breath.

"Okay," I said.

"No." It came out more quickly than I would have liked, and I caught the look Will gave me.

Below us a coach stopped to disgorge another load of visitors outside the castle gates. We watched in silence as they filed out of the vehicle and into the old fortress in a single, obedient line, primed to stare at the ruins of another age.

"Something like that." I began to gather up our things. "Let's just go back to the house."

"You claustrophobic?"

I didn't like being awake at night. I couldn't help but wonder whether Will was awake, on the other side of the castle, and my imagination kept prising my way into his thoughts. It was a dark place to go to.

The following weekend, I came down in the middle of the night to fetch some water. I had been having trouble sleeping, and had found that actually getting up was marginally preferable to lying in my bed batting away the swirling mess of my thoughts.

Here was the truth of it: I was getting nowhere with him. Time was running out. I couldn't even persuade him to take a trip to Paris. And when he told me why, it was hard for me to argue. He had a good reason for turning down almost every single longer trip I suggested to him. And without telling him why I was so anxious to take him, I had little leverage at all.

I was walking past the living room when I heard the sound -- a muffled cough, or perhaps an exclamation. I stopped, retraced my steps and stood in the doorway. I pushed gently at the door. On the living-room floor, the sofa cushions arranged into a sort of haphazard bed, lay my parents, under the guest quilt, their heads level with the gas fire. We stared at each other for a moment in the half-light, my glass motionless in my hand.

"What?"

"We fancied a change." My mother glanced at my father for backup.

"But you can't sleep down here! You can't be comfortable like this."

"We've given Treena our bed," Dad said. He was wearing an old blue T-shirt with a rip in the shoulder, and his hair stuck up on one side. "She and Thomas, they weren't getting on too well in the box room. We said they could have ours."

"Go on back to bed now, Lou. Go on. We're fine." Mum practically shooed me away.

My father, the great lump, couldn't meet my eye.

I walked back up the stairs, my bare feet silent on the carpet, dimly aware of the brief murmured conversation below.

My mother pushed herself up on to her elbow. "Ssh. Don't raise your voice. We…" she looked at my father. "We fancied a change."

And then, as I stood, dumbly struggling to comprehend, he added, "It's only at weekends. And you can't sleep in that box room. You need your sleep, what with…" He swallowed. "What with you being the only one of us at work and all."

"What -- what are you doing there?"

"We're fine, love," Dad said. "Really."

There were seventy-nine days left on my calendar. I started to feel anxious again.

I hesitated outside Mum and Dad's room, now hearing what I had not heard before -- Thomas's muffled snoring within. Then I walked slowly back across the landing to my own room, and I closed the door carefully behind me. I lay in my oversized bed and stared out of the window at the sodium lights of the street, until dawn -- finally, thankfully -- brought me a few precious hours of sleep.

And I wasn't alone.

Mrs Traynor had waited until Nathan was taking care of Will one lunchtime, then asked me to accompany her to the big house. She sat me down in the living room and asked me how I thought things were.

"Well, we're going out a lot more," I said.

"I really don't mind," she said, "if you want to go somewhere. I know we probably weren't the most enthusiastic advocates of your idea, but we've been talking a lot, and we both agree…"

She nodded, as if in agreement.

"He talks more than he did."

"To you, perhaps." She gave a half-laugh that wasn't really a laugh at all. "Have you mentioned going abroad to him?"

"Not yet. I will. It's just… you know what he's like."

"Yes, it was my birthday. My parents were doing a special dinner."

"So -- Will tells me he went to your house."

We sat there in silence. She had made me coffee in a cup and saucer. I took a sip of it. It always made me feel about sixty, having a saucer balanced on my lap.

"How was he?"

"Good. Really good. He was really sweet with my mum." I couldn't help but smile when I thought back to it. "I mean, she's a bit sad because my sister and her son moved out. Mum misses them. I think he… he just wanted to take her mind off it."

Mrs Traynor looked surprised. "That was… thoughtful of him."

She stirred at her coffee. "I can't remember the last time Will agreed to have supper with us."

"My mum thought so."

She probed a little more. Never asking a direct question, of course -- that wasn't her way. But I couldn't give her the answers she wanted. Some days I thought Will was happier -- he went out with me without a fuss, he teased me, prodded me mentally, seemed a little more engaged with the world outside the annexe -- but what did I really know? With Will I sensed a vast internal hinterland, a world he wouldn't give me even a glimpse of. These last couple of weeks I'd had the uncomfortable feeling that hinterland was growing.

"I couldn't reach him. I couldn't get anywhere near him." She placed her cup and saucer on her knee. "He's a singular person, Will. From the time he hit adolescence, I always had to fight the feeling that in his eyes I had somehow done something wrong. I've never been quite sure what it was." She tried to laugh, but it wasn't really a laugh at all, glancing briefly at me and then looking away.

"Not all of them."

"I think so."

I pretended to sip my coffee, even though there was nothing in my cup.

"He seems a little happier," she said. It sounded almost as if she were trying to reassure herself.

Mrs Traynor gazed out of the windows, to where her precious garden had begun to bloom, its blossoms a pale and tasteful melding of pinks, mauves and blues.

"Yes," I said, then added, "it's my sister who drives me nuts."

"Do you get on well with your mother, Louisa?"

"It has been very --" her gaze flickered towards me " -- rewarding, to see him a little more like his old self. I am very well aware that all these improvements are due to you."

I let myself out.

"We have just two and a half months." She spoke without turning her head.

Leo McInerney died on 22 May, in the anonymous room of a flat in Switzerland, wearing his favourite football shirt, with both his parents at his side. His younger brother refused to come, but issued a statement saying that no one could have been more loved, or more supported than his brother. Leo drank the milky solution of lethal barbiturate at 3.47pm and his parents said that within minutes he was in what appeared to be a deep sleep. He was pronounced dead at a little after four o'clock that afternoon by an observer who had witnessed the whole thing, alongside a video camera there to forestall any suggestion of wrongdoing.

"I know, Louisa." She nodded.

I put my coffee cup on the table. I did it carefully, so that it didn't clatter. "I'm doing my best, Mrs Traynor."

She and Leo's father had been interviewed three times by police and faced the threat of prosecution. Hate mail had been posted to their house. She looked almost twenty years older than her given age. And yet, there was something else in her expression when she spoke; something that, alongside the grief and the anger and the anxiety and exhaustion, told of a deep, deep relief.

"He looked at peace," his mother was quoted as saying. "It's the only thing I can hold on to."

"He finally looked like Leo again."