'We can.'

She put her arms around his neck, and kissed him. His response was an unexpected dip, which elicited another squeal from her. But then they were dancing, holding tight to each other, suddenly oblivious to their surroundings.

'I remember the first time we danced,' he whispered into her ear. 'Do you?'

'Of course. I remember the song, and what you were wearing, and how it felt.'

'And I remember the last time, too.'

Cranwell. At the ball. She didn't remember the song. Just the feeling. The sad, horrible feeling that it was all ending ...

'It wasn't the last time, though, was it? We're dancing now, aren't we?'

And we were each other's first, Susannah thought, as she nuzzled his neck. Before we belonged to anyone else, we were each other's.

It couldn't last, of course. They both knew it. Not the evening, not the holiday. They danced until Susannah's feet started to hurt, then Rob drove them back to the house. They fell asleep wrapped in each other's arms, and slept soundly.

The next morning, when she checked her BlackBerry, there were emails, texts and voicemails from Douglas, each barely containing his irritation.

Where the hell are you?

She couldn't bring herself to reply.

Her return flight was already booked for that evening, and she knew she had to go home.

She had to be at work.

She had to get back to her life.

They hadn't had enough time.

She had to return the hire car, so Rob couldn't even take her to the airport. He came anyway, following her car in his own, and parking in the big car park in front of the terminal. The flight was displayed, and there was no queue at check-in. Rob went all the way to passport control with her, and then held her tightly in his arms before she went through.

Susannah felt strangely tearful. 'This is stupid I'm going to see you in two days. I don't know what I'm making all this ridiculous fuss for. I feel as if, I feel ... I'm just afraid of what is coming, I think.'

'Don't be. I'll call you in the morning. And I'll be back by the weekend. We can see each other then.'

'Promise?'

'I promise.'

She had hoped the house would be empty when she got back. She wanted the chance to sort herself out before Doug came home. But the flight was delayed an hour, of course, and the traffic was terrible coming in from Gatwick, and she saw, with a slightly sinking heart, that the lights were on when the minicab pulled up at the front door. Doug came to the door while she paid the cab, and took her case from her hand, kissing her cheek. He only had socks on his feet, and he'd taken his tie off.

'Drink? I'm having one.'

'Thanks.'

He poured them both a tumbler of whisky and went through to the kitchen to get cubes of ice from the freezer, dropping each one in slowly and deliberately. 'So, where did you go?' He sat down and slid one glass across the table to the place opposite.

Susannah pulled out the chair and sat down. 'France. To Mum and Dad's.'

He nodded, as though he wasn't really listening. He wasn't really looking at her either. 'We had a really interesting internal memo come round ... oh, when was it? A week or so ago. Two, maybe.'

She didn't know what he was talking about. He was acting strangely. She felt trembly and anxious.

'It was for the family law guys really. Not us. But they circulate most of these things to everyone. Ignorantia juris non excusat and all that. Probably a salutary warning, too.'

'What are you talking about, Doug?' She'd always found it irritating when he used Latin phrases. It made him sound pompous.

'It was really fascinating, actually. Apparently texts and emails are the new private eyes. You know you want to catch someone out, catch someone red-handed, doing what they oughtn't to be doing it's all there now, in black and white, and emoticons and hard discs. So this was a memo outlining the use of this kind of information in cases you know, divorces, custodies, that sort of thing.'

'Oh.'

'So, I was wondering, Susannah. If I could hack into your email account. If I knew your BlackBerry's passcode. And I mean ... I know this is all hypothetical. I can barely switch the computer on. Can't programme the video. Utterly useless at all that stuff. But if I could ... If I could see all that, would I catch you ... catch you doing something you oughtn't to be doing?'

'Douglas '

He interrupted her. 'Because, you see, I know there's something. Something not right. Something going on. Something different. And now I'm thinking to myself. You disappear on me no explanation, no number to call. Maybe there's someone.' He looked right at her now. 'Is there, Susannah?'

Even as her heart pounded and ached, and bile rose in her throat, there was some relief. She nodded, slowly.

Doug took a deep breath and put his elbows on the table, leaning his chin on his hands.

Susannah waited.

Redness spread across his neck, but his voice was calm. 'And do you love this person?'

Again, she nodded. 'I do.' She thought he would ask who it was. How they'd met. Whether she'd slept with him. All the obvious questions. She was ready to answer them all.

But he didn't ask. Anything. He sat for another moment or two, then he downed the contents of his glass, pushed his chair back from the table and stood up.

This she hadn't expected. 'Doug. Can we talk about this?'

He shook his head, as though a fly was bothering him, his movements sharp and rapid. 'I don't think we can. Not tonight.'

She didn't turn round as he left the room. She heard his footsteps on the tread of the stairs, heard him close the door to his study and then the muffled sound of the Dave Brubeck Quartet coming through the walls.

He didn't come out again that night, and he'd gone by the time she woke up the next morning after a fitful, anxious night where it felt as if she had woken up on the hour. All she wanted to do was talk to Rob. But she couldn't do that. What was it Rob had said, in France? It felt 'disloyal'. The kissing, the touching, the desire and the longing that all felt right, because it obliterated everything else. It was the talking that felt disloyal.

Doug hadn't come into the room they shared that night he must have taken the clothes he needed for work before he went up, and then showered in the guest bathroom this morning. Or at the gym. She hadn't heard the water running. Although she'd had a dreadful night. She'd got up around three and taken a pill, but she still hadn't fallen into a deep sleep until after five, and the alarm went anyway at seven, dragging her back from a thousand miles away.

Doug didn't want to see her. He couldn't stand to see her.

She couldn't stay, not after that. It was unbearable. And it wasn't fair. In a way, he'd made it easier for her, by guessing. But it didn't feel easier. The unpicking of something she'd been putting together for nine years felt anything but easy. Everything that had felt so wonderful in France under the cobalt-blue sky felt wretched under England's grey clouds. What had seemed pure was now tainted.

She told herself, sitting on the underground, that she hadn't set out to hurt Douglas. That he'd hurt her. She told herself there were wide cracks in their relationship too wide and too jagged to repair long before the June day last year when she'd seen Rob, and maybe seen her future, across the common. She should have left years ago.

But she hadn't. She'd stayed because it was easier than the alternative better than being alone. Because she'd hoped she could make it better, hoped he'd change, hoped she'd love him again, love him more.

She'd stayed in part for the kids. They were the only kids she had, as imperfect and flawed as their relationships were. They were the kids she'd settled for. And only now, only just now, had those relationships started to flourish. It felt cruel to her, and she knew it would to them, too. Daisy and Rosie.

And now leaving was so much harder.

She went to work to answer emails and return phone calls. Megan peered curiously at her and told her she looked like death warmed over. She said there was obviously a reason Susannah never took all her vacation days time off didn't agree with her. Susannah thought of her glowing, happy reflection in the mirror in her parents' French bathroom, and readily agreed, claiming she'd eaten something funny on the plane home and that she needed to go home to be near the loo and sleep it off.

At home, she'd packed the biggest bag they had by the time Douglas came home, and brought it downstairs. It was by the front door, and he saw it as soon as he came in.

He rubbed his eyes, and when he spoke his voice was tired, and annoyed. 'Here we go again. Where this time? Or aren't you saying?'

'Can you come and sit down, Douglas? Can we talk? I wanted to talk to you yesterday, but you wouldn't let me. Let me now. Please.'

'I don't want to sit down, Susannah. I don't much want to talk, to be honest with you. Not this time. I just want to know what's going on.'

She sighed. 'I'm leaving.'

'I can see that.'

'No. Leaving. Leaving you. For good.'

He did, at least, appear to be shocked. He put his coat and briefcase down at last, and stepped into the living room, sitting down on the nearest chair. 'Because of him?'

Susannah sat down opposite him. It should be obvious. 'Because of you and me.'

'I don't believe you.'

'You should. I'm telling you the truth. I told you about him, and you've no other reason to doubt my honesty. It isn't because of him. That makes it sound like I'm leaving you for him, and that's not what I'm doing. I'm leaving you because this relationship isn't working. It hasn't been working for a long time. And I've known it. You'd know it too, if you were honest with yourself. And I've been a coward. I should have left a long time ago. A long time, Douglas. It's not him.'

'But that's where you're going, isn't it? That's who you're going to be with?'

'I don't know.' That was true, too.

He was staring at her, hard.

'I hope so.' She wouldn't lie to him about it.

'Shit.' Douglas was shaking his lowered head, and his breath was coming in gasps.

'I'm sorry, Doug.'

'Don't do it.' He suddenly slid forward, off his chair, on to the floor in front of her, almost putting his head in her lap. 'I don't want you to go.'

Of all the reactions she might have predicted, this was the least likely scenario. She'd expected anger, or some sort of resigned agreement. Not this. This wasn't like him.

'I'm sorry, Susannah. I'm sorry I haven't been who you want me to be. That's it, isn't it? I have been letting you down.'

She was tired, but it wasn't going to work this time.

'I can be, though. That's the thing. I can be that guy. I can change. You just have to tell me what you want.'

'That's the point, Doug. I shouldn't have to tell you. I shouldn't need to ask. If it was right, I wouldn't have to. Nor would you. Can't you see that? It's wrong.'

He shook his head. 'I don't accept that.'

Susannah stood up.

He remained, slightly foolish, on the floor at her feet. It was strangely undignified, and she was glad when he stood up slowly and looked her in the eye.

'You have to. This is happening. I don't want ... this ... any more, Doug. None of it. I don't want you. I don't love you. Not like that.'

They stood, facing each other, in silence, until Susannah couldn't bear it any more. She half shrugged in apology? In resignation? And then, as calmly as she could, all her movements slow and deliberate, she took her raincoat from the chair, picked up her bag, and walked to the front door.

All the while, Douglas stood and watched her, his arms by his sides, palms turned towards her and slightly raised, as though he were about to conduct an orchestra. She closed the door at last, quietly, behind her, without a word, and went to her car, walking faster now she had left the house.

Douglas didn't come after her, but she pushed down the lock on the door anyway. Her hands trembled uncontrollably as she turned the key. She pulled out abruptly, without looking in her mirrors. Behind her, she heard the screech of a car's brakes, and the driver pounded hard on his horn in fear and anger. Susannah's heart was throbbing in her chest, and she was breathless. She half raised a hand in apology and, taking the next left turn, indicated and pulled into a space. She turned the ignition off and put her head on the steering wheel, trying to concentrate on making her breaths long and deep.

She couldn't believe she'd said it. She was stunned to have walked away, in an instant, from the past nine years of her life, since she'd first met Doug. There was nothing like relief in it at this moment, although she had to believe that would follow she'd been thinking about this, knowing she had to do this, for so long. But for now, she felt sick and dizzy. She closed her eyes, and tried not to think.

When she raised her head, the clock told her twenty minutes had passed. The palpitations had slowed. She didn't know what to do next. In all the imagining, she'd never followed herself out of the door. The daydream had stopped when she walked away. She thought about Amelia, or her parents. She didn't want to be alone. It was getting late.

But when she pulled out again, this time taking care to look carefully behind her, she headed with absolute certainty towards the only place she could imagine going: she headed towards him. Even if it was wrong, even if it was betraying Douglas, and even if he didn't want her there, she headed towards him.

She had never been to Rob's home before, although she knew exactly where it was. He'd lived there with Helena, and she hadn't wanted to before. She hadn't wanted to see, or acknowledge a home that the two of them shared. A kitchen they cooked in, a bed they slept in. A life they'd built. Now she didn't care didn't care if it was theirs, didn't care if it was selfish.

Rob answered the door with his face full of concern. It was after 10 p.m. now, she realized, and she hadn't called ahead. He can't have been back long. He must be exhausted from the driving.

'I ended it.'

That was all she could say. She had no idea until the moment she stood in front of him how exhausted she was. She'd barely slept at all the night before, and she realized she hadn't eaten today, and now, standing here, she thought she might fall down.

Rob didn't say anything. He just opened his arms, and folded her into his embrace. She let her whole weight rest against his bulk. His hand held the back of her head, and she felt his lips in her hair, silently kissing her head. She was trembling.

He half carried, half dragged her into the living room, and then sat her gently on the sofa, leaning her against the cushions, as if she was a child. He took off her shoes, and she curled her legs up under her. He pulled a throw over her. News at Ten was on the television, and the Times lay open on the arm of a chair, next to a whisky tumbler, still half full. Susannah closed her eyes gratefully, his hand smoothing her fingers.

He passed her the glass and watched her drink it straight down. 'Tea?'

She shook her head. She just wanted to close her eyes. She was profoundly grateful he wasn't asking her questions. She had never felt so tired in her life ... he sat on the arm of the sofa, stroking her head gently, and they watched the end of the news, and the weather, without any words at all. It was a weirdly domestic situation, both of them quiet, and calm, for the first time in a long while.

She had no idea when she fell asleep.

When she woke up, the digital display on the television said 5.00 a.m., and she was alone in the living room, still under the blanket. For a gentle, blissful moment, she didn't remember where she was. Or anything that had happened. She existed in the wonderful state of nothingness that adults have for the first minute or so of their day. And then she remembered Doug's face as she left, Rob's arms around her when she'd arrived on his doorstep.

The memories came in waves.

She sat up and pushed her hair behind her ears, rubbing her eyes.

Rob was in bed, in his room at the top of the stairs. He'd left the door wide open. He'd fallen asleep half sitting up, with the side light on, and there was an open book on the sheets next to him. He was wearing an old khaki T-shirt with a hole at the neck, and it had ridden up to reveal his slim, muscled stomach, and the dark hair there. For a moment she stood by the bed and just watched him, watched the gentle rise and fall of his chest as he breathed, watched his eyelids flicker slightly in his dreams. It felt as if she'd loved him all her life. Susannah silently picked the book up and closed it, put it down carefully on the bedside table. She reached down and switched the bedside light off. It was already just beginning to get light outside, and the early light cast a softer glow on the room. She slipped her dress over her head, and pulled her bra and underwear off, then she slid quickly under the sheets to lie beside him, naked. She laid her head on his chest, and rested her forearm on the side of his stomach. She thought she might go back to sleep in his arms, and stifled a yawn.

But he began to respond to her before he was anywhere close to awake. One arm snaked slowly around her shoulders and the other pulled her up on to his stomach, so that she was almost lying, naked, along the whole length of him. His hands travelled luxuriously, languorous and sleepy, down her back, and cupped her behind. Unconsciously his hips began to push rhythmically, gently, into her, and she felt him begin to harden beneath her.