Katie put down the plates and moved over to the rug. Mia budged up and they lay together. Katie could smell wool and damp earth. Rolling onto her side, she bared her teeth: 'Gone?'

'Gone.'

Clouds were starting to break up the wide expanse of blue and she imagined that in another hour the sun would be swallowed. 'Are you coming home for the summer, after finals?'

'My housemates are doing MAs. I may stay on, too.'

'To do what?'

'Drugs. Prostitution. Theft.' She sighed. 'I don't know, Katie. There is no grand master plan.' She ran her fingers through her hair and Katie caught the smell of woodsmoke in it.

'If you want me to look for vacancies on our system, I can do. They'd be in the city, though.'

'Christ, the thought of London in the summer suits, office blocks and clammy Tubes I'd go mad.'

'Seven million Londoners manage.'

'Maybe I'll spend the summer in Europe.'

Katie laughed.

'What?'

'How are you planning to pay for it? You're at your overdraft limit and you still owe me 500.'

'Thanks for the financial advice.'

'Really though, Mia, I would like my money back soon.'

'What, that big salary of yours just isn't enough to keep you in calendars and highlighters?'

A cloud passed overhead, blocking out the sun. 'You can be so sharp sometimes.'

'And you can be so predictable.'

Katie stood, smoothed down her dress and crossed the lawn. She gathered the stack of plates in one arm and picked up the tray of potatoes in the other.

'And now you're going to do all the clearing up, so I look like the arsehole.'

With a hangover, Mia was most often sullen, but occasionally vicious. Katie wouldn't rise to it. She moved indoors, her eyes adjusting to the gloom. The kitchen smelt of garlic and rosemary and a play was in full swing on the radio. She scraped the leftovers into the composter and then searched beneath the sink for the washing-up liquid.

Mia stalked in, setting down a serving dish with a clang. She snatched off her sunglasses and then yanked open the dishwasher and began forcing the plates into the rack.

'That's clean. It needs unloading.'

With a sigh, she dragged the plates back out and banged them down on the side.

'Mum's asleep.'

'There I go, fucking up again.'

Katie ran hot water into the sink and added a squeeze of washing-up liquid. 'We're getting too old for this, Mia.'

'For what?'

'For this fights over nothing. We're only together a handful of times a year I just don't need it.'

'And I don't need you telling me what I should be doing with my money, and how I should be living my life.'

Katie laughed, shaking her head, and the gesture only enraged Mia further.

'You think you're so fucking superior, don't you?'

There was a knock at the back door and Finn walked in with a cheery, 'Hello!' His arrival did not deter Mia, who blazed on: 'You must love hearing about my spanked overdraft and my "aimless" future. But fuck, Katie, you know what? I don't want your corporate bullshit job, your swish pay packet or your pretentious London dinner parties. I don't want to be anything like you, because I look at you and think one thing: Safe.'

The word wounded her with its connotations of cautiousness, predictability and conservatism.

'Aren't you going to say something?' Mia goaded, eyes dancing. 'Tell me what a bitch I am?'

Katie turned off the tap and faced her sister. 'You don't need me to tell you that.'

Mia glared at her, then pushed through the back door, letting it slam behind her.

Katie could feel tears beginning to prick her eyelids and she turned back to the sink, slipping her hands into the soapy water.

'I'm sorry,' Finn said behind her. 'She doesn't mean it.'

'No?' At the edge of the kitchen, Katie heard the washing machine click into its spin cycle, a button or zip striking the drum with each rotation. 'I love her,' she said quietly, 'but sometimes I don't think I know her. That's a terrible thing to admit, but it's true. I honestly don't know my own sister.' She looked up at the ceiling but couldn't stop the tears spilling onto her cheeks.

She felt Finn's hand on her shoulder as he gently turned her towards him and wrapped his arms around her.

She had known Finn since he was 11; they'd hidden in the boiler cupboard together, crouching on a mound of warm towels waiting for Mia to find them; he had given her a piggyback home when she'd sprained her ankle chasing Mia's runaway kite; they'd kissed cheeks when she'd arrived at Mia's 21st birthday; but Finn had never held her in his arms like this. She had always thought of him as a boy, her little sister's friend, but as she let her head rest against his chest and her soapy hands lock over the hard muscles at his back, her perception began to shift.

She felt his heart beating against hers and wondered if he was attracted to her. She imagined Mia walking into the kitchen and witnessing this moment and the thought thrilled her. She breathed in the warm smell of his skin and then, very slowly, she lifted her face towards his.

The kiss was gentle, an exploration of the idea, their lips lightly brushing before sinking more deeply into the softness of one another's mouths.

On the train back to London the following day she leant her head against the carriage window, watching Cornwall disappear in flashes of greens and blues, but the memory of the kiss travelled with her. That week she called Finn and they met after work for a drink. It was a scorching day and they sat at a pavement table in Covent Garden, Katie drinking white wine and eating olives with her fingers, and Finn sinking cold beers. They watched workers loaf by with rolled-up shirtsleeves and loosened ties; the glow of summer's arrival spread in Katie's chest, and her laughter felt honest and real. They ordered grilled chicken and roasted sweet potato, and moved inside when the sun dipped behind the buildings.

Over the next month they saw one another regularly. With Finn, she discovered parts of London she'd never experienced: picnicking beneath a monkey puzzle tree in Battersea Park; joining a free walking tour of haunted buildings; eating sushi in a basement restaurant in Bank. They made love in his rented flat, Katie amazed at the way her body arched and hungered for his touch.

And then there was Mia. She had not made contact with Katie or Finn since their fight. It was no surprise; she'd always struggled to frame an apology but this time Katie was grateful for her sister's silence, as it meant she didn't need to confront what was happening between herself and Finn.

One Sunday afternoon, Katie was walking with Finn in Hyde Park, their fingers threaded together. They were musing on what to do for dinner when Mia called him.

'Hey,' he answered casually, letting go of Katie's hand. 'It's good to hear from you ... fine, thanks ... sorry, I've just been busy ... No, of course not! ... In Hyde Park, taking a stroll ... Yeah, it's hot. I'm in shorts ... No one's fainted, yet ... No, I'm with Katie.'

When Finn glanced round, she saw his neck was beginning to redden.

'No, we arranged it,' he said, placing a hand to his ear to block out the noise from a group of passing students. 'We've been seeing a bit of each other ... Kind of ... I am being serious ... About a month or so ... Well, yes ... I guess we are.'

Mia must have been talking then for a long time as Finn just seemed to shake his head and say, 'It's not like that ... Come on, Mia ... That's not fair ...' Eventually he held out the phone to Katie. 'Your turn.'

She pressed it to her ear and heard Mia's voice, low, deadly, distilled by outrage. 'Is this a joke?'

'No,' Katie said levelly. 'It isn't.'

'You and Finn are what ... a couple?'

'Yes.' She felt a flutter of excitement at the word.

'I don't believe this!'

Katie glanced over her shoulder and saw that Finn was hanging back, giving her space. 'We just I don't know get on.'

'He's my best friend.'

'So be happy for him.'

'We both know you're doing this to get back at me.'

It was true that at first she'd felt a private triumph over Mia, but there was no satisfaction in it now. 'I care about him,' she said, trying out the words.

'Bullshit. You spent our teens telling me what a fuckwit he is.'

That was also true. He had been the scapegoat for everything that was wrong in her and Mia's relationship. 'We were kids. Everything's different now.'

'Isn't it just?'

Six weeks passed and she didn't hear from Mia. It was bad news that finally brought them together. Their mother had called them both home to tell them that the dizziness and headaches she'd put down to exhaustion were, in fact, cancer.

Mia struggled to cope with their mother's illness. She visited home even less, drank and partied with renewed energy, and was fuelled with enough anger to refuse all of Katie's calls. Finn couldn't get through to her either; Katie knew he emailed her every week, but never got any reply. Without him, Mia was like a compass that had lost its magnetic field and was spinning, directionless.

In the end, Katie felt there was no choice. Mia was her sister: she had to come first. Katie finished her relationship with Finn four months and eight days after it had begun. She did it in a bar in Clapham so he couldn't hear her voice waver when she lied, telling him, 'It's been a lot of fun, but I think it's run its course.'

Finn had risen from their table and drifted out of the bar, hurt. Immediately she knew that she'd made a dreadful mistake. She loved Finn. He made her happy. It was too big a sacrifice to make. She had grabbed her coat and raced through the bar after him. But by the time she reached the street, he had gone.

Mia and Finn's friendship quickly returned to its former shape and, eventually, she and Mia came to their own kind of truce although it took their mother's funeral to thaw their anger. When the hearse arrived, Katie found Mia hovering on the upstairs landing, her fingers resting at the edge of a framed photo. In the picture, their mother was wearing a salmon-pink sundress, the hem lifted around her knees by a breeze. She was glancing over one shoulder, smiling with a hand shading the sun from her face. Two soft laughter lines bracketed her smile like dimples.

'She was beautiful,' Katie had said.

Mia turned. Her face looked so drawn against her dark hair and flowing black dress that she seemed haunted. 'I should have asked her where this was taken. What she was smiling at. I should have asked.'

That was when Katie had stretched out her arms and Mia had fallen into them. They remained like that until they heard the hearse driver clearing his throat downstairs.

'Just to let y'know,' the waitress said, startling Katie out of her reminiscences, 'I'm closing up in a few minutes.'

'Yes. Of course. Sorry,' she said, shutting the journal and getting to her feet. She rummaged in her purse and found a $5 note, leaving it as a tip to apologize for holding up the waitress.

Outside, the evening was thick and warm, a small surprise after the air-conditioned coolness of the cafe. She drifted along the street, the journal tucked at her side, her thoughts still circling around Finn.

When she had dropped Mia off at Heathrow, it was the first time she'd seen Finn in months. She had worked hard to avoid him, and anything that reminded her of him. She no longer listened to Capital Radio, the station where she'd helped him get placed as a junior producer, or walked the North Carriage Drive in Battersea Park that took her beneath the monkey puzzle tree where they'd once sat.

She congratulated herself quietly on the success of her efforts, but the moment she saw him strolling into the airport to meet Mia, his backpack slung off one shoulder, Katie knew she was undone. It was the smallest details that did it: the fine lines at the corners of his eyes that spread like sun rays as he smiled; the lightness of his tone as he asked, 'Coming with us?'; the smell of soap on his skin as he kissed her goodbye.

As she drove away from the airport, the passenger seat empty, her mobile rang. For an absurd moment she imagined it was Mia or Finn telling her to turn the car around and come away with them. But it was Ed. She shoved the phone into the glove compartment and turned up her music. Instead of returning to the flat, she found herself peeling off the M25 and following signs to the west.

She drove for five hours straight and arrived in Cornwall with stiff arms and the beginning of a tension headache. She parked outside her family home and was pleased the new owners weren't in so no one could see her wandering across their driveway, trailing her fingers through the lavender bushes their mother had planted.

Afterwards, she'd driven to Porthcray and walked the cliff path, her heeled shoes feeling cumbersome on the rutted, windswept track, and that's where she cried. Thick, gasping sobs escaped into the breeze and were blown out to sea.

Sometime later she had dried her eyes, filled the car with petrol and then driven straight back to London.

Now she paused on the street, lowering herself on a squat brick wall to rest. She wondered where Finn would be right now. London? Cornwall? Another country, even? Had he found a new job? Did he think about Mia every day, the way she did? Did he think about her?

She regretted her behaviour at the funeral. It was inexcusable. She had lashed out and slapped him: not because he had returned home without Mia, but because he had left with her in the first place.

18.

MIA.

Western Australia, February Mia felt the warmth of the sun on her cheek, heard a pleasing watery glug in the distance, smelt salt carried to her on the breeze. She opened her eyes a fraction and a spectrum of colour danced at the edges of her lashes. She raised a hand to shade the sunlight from her eyes, blinking as the world came into focus. Blue sky. Sea. An empty horizon. Red slabs of rock.

She had slept on the rocks.

With Finn.

She inched her head to the side, feeling a new stiffness in the muscles of her neck. Finn lay next to her folded into his sleeping bag, one arm flung out to the side. His lips were parted and his breathing was slow and shallow. The low sun illuminated the clear pores across his nose and the stubble grazing his jaw, which was light brown with a hint of amber nearest his lips.

She was jolted by a sudden memory: his lips on the inside of her arm. Then came other images: her mouth covering his; the length of Finn's back beneath her hands; a glimpse of his tongue as he ran it over her nipples; her teeth against the soft flesh of his shoulder.

She slithered from the sleeping bag, naked. The air was cool. Swiftly but quietly she slipped on her underwear and pulled her dress over her head, not minding that it was inside out. As she bent to grab her flip-flops, her foot clipped the empty bottle of rum. She froze. It bounced and clattered over the rocks, eventually coming to rest in a crevice, unbroken.

Finn shifted. He rolled onto his back and hooked an arm in front of his face but didn't wake. She studied him for a moment and then she turned and picked a pathway over the rocks with her flip-flops held out at her side. She jumped down onto the hard-packed sand and began to jog. Her head pounded but she pushed herself on, trying to shake off the deep uneasiness spreading through her stomach.

She veered into the shallows, water spraying her bare legs and soaking the back of her dress. She was running hard and it felt as though her head might explode from the pain. She curved away from the shore, picking a sandy path that wove over the heath towards the town.

The scrub was sharp against her feet, forcing her to put on her flip-flops. As she straightened, she glanced back to the rocks and saw that Finn's sleeping form was only a speck against the empty landscape. It was wrong to have left him; he would worry when he woke and found her missing, but how could she stay?