A boy.

'No.' I grab Franny's arm. She must be mistaken. 'Maybe it was a little girl with a short haircut . . . young children can look-'

'No way,' Franny insists. 'He was wearing a Woodholme sweatshirt. It's a boys' school.'

I blink rapidly, trying to make sense of what she is saying.

'But you said you saw them the Saturday before last,' I say, shaking her arm. 'Why would he be wearing school uniform at the weekend?'

Franny frowns. 'Woodholme's a private prep school. I've got friends who went there. They do Saturday school.'

I let go of her arm, the sick feeling in my stomach raging up into my throat. My heart is racing so fast I feel like I might keel over. The van has disappeared into a black blur at the edge of my vision. I'm going to be sick, I'm sure of it.

I don't understand . . . it doesn't make sense . . . my baby is a girl . . .

And then the black blur mists up in front of my eyes and I pass out.

'Gen?' It's Lorcan's voice. 'Gen, are you okay?'

Fingers are smoothing damp hair from my wet face. The ground is cold under my body, raindrops falling in a mist.

I open my eyes to find Lorcan gazing anxiously down at me. 'Gen?' he says.

'I made a mistake,' I said. 'It isn't Beth at all, it's some other child.'

'What?' Lorcan frowns. 'What are you talking about?'

I struggle to sit up. The back of my head is sore where I must have banged it and I still feel sick. I lean over my knees, letting the nausea ebb away. I've only fainted once in my life before at a bar on my hen night. I'd barely eaten anything during the weeks leading up to the wedding and I couldn't cope with all the booze. It was Hen who looked after me then insisting I went straight home with her in a taxi. My wedding was a few days later. Hen stood with me, my only bridesmaid. It feels like a lifetime ago.

I breathe out slowly, feeling the nausea pass. 'Where're Bobs and the girl from the shop?' I mumble.

'Inside.' Lorcan strokes my back. 'When I saw you faint, I rushed out here and Bobs called Franny in then bolted the door, put the Closed sign up and disappeared through to the back.'

I look at him.

'I know.' He grimaces. 'That guy is guilty as hell about something. God, you look pale,' he says, wiping rain off his face. 'Can you stand up? Are you hurt? Let's get you in the car.'

I let him help me to my feet and over to the car. I sit inside, shivering in my damp clothes. Lorcan reaches round and grabs a fleece from the back seat.

'Cover yourself with this,' he orders.

I drape it over my wet coat and lean back against the headrest.

'What did you mean, it was a different child?' Lorcan asks.

I explain what Franny told me. 'So you see, it's a boy. Not Beth. Not my Beth.' I close my eyes, trying to let this revelation sink in. I honestly believed I was getting close to an understanding of what had really happened to her, and now I'm as far away as ever.

'A boy?' Lorcan frowns. 'How does that fit?'

'It doesn't.' I gulp as the shocking enormity of Art's deception rises inside me again. 'Art must have had someone from the beginning . . . from before he even met me. A whole other life . . . family . . .'

My thoughts dart back to Hen. Of all my friends, she has known Art the longest. She has talked to him behind my back and kept things from me and she has a son the same age as Beth would have been. She might be married to Rob now, but is it possible she has some kind of double life with Nat and Art down here? I can't for the life of me see how it could be so, but . . .

'Maybe it's someone I know,' I say. 'Someone I've known for a long time.'

'No.' Lorcan shakes his head. 'I'm sorry, Gen, but that's crazy. Think about it. When you met him Art was completely obsessed with his business, wasn't he? Even if he has a second family now, there's no way he had time for one back then.'

'Then it's her child and Art comes to see them both. Either way, Art has another family. Maybe it's Charlotte West. She lives near here, after all. And I know she called Art all those times. Jesus, she came to our house and he was pissed off with her. Maybe they were together then it finished and now she's stalking him.' I realize my fists are clenched, and release them.

Lorcan makes a face. 'I don't know, it sounds very convoluted. I mean, if Art really does have someone else, why stay in his marriage?' He spreads his hands on the steering wheel of the car.

'I don't know.' I close my eyes. 'All I know is that the child Art comes here to see isn't Beth.'

'Wait a second,' Lorcan says. 'Suppose it is "Beth"? Suppose they made it up?'

'Made what up?' I open my eyes. What is he talking about? 'You can't pretend that a girl is really a boy, not all the way to eight years old. The school would know for a start and-'

'I don't mean that Art and the other woman made up Beth was a boy,' Lorcan explains. He runs his hands through his damp hair. 'Suppose they made up Beth was a girl? Suppose, in fact, your baby was a boy all along?'

I think through the list of people who were at the birth. Apart from Art, there's Rodriguez and Mary Duncan and the anaesthetist. I think back to the conversation I had with Mary's sister, Lucy O'Donnell. She definitely referred to "Beth", but then she also said that she'd "found out" my baby's name when she looked me and Art up online. Maybe Mary never specified whether I'd had a boy or girl. She was dying when she confessed, after all. What was it she'd said exactly? I wrack my memory.

'Her baby was born alive . . . I feel . . . so bad for that poor lady because they took her baby away and told her the little thing was dead.'

'Why lie about the sex of a baby you were telling everyone was dead anyway?' I rub my head. It still feels sore.

'To cover their tracks.' Lorcan says. 'It's an extra layer of protection . . . an extra barrier to stop people ever finding the baby. And the child Art has been seen with is the same age as Beth would be now . . .'

I stare at him, a mix of confusion and hope mingling in my head. I can hardly bear to face the idea that the daughter I lost, the Beth I've been dreaming of, is a fiction. It's too much. For the past eight years I've imagined her: my little girl. I've pictured her, I've mourned her, I've even dreamed her. She was so real to me. And now I'm being told the very fact of her is an illusion.

'We have to go Woodholme School,' I say. 'I need to see this boy . . . I need to see for myself.'

Half an hour later we're parked outside a high brick wall, softened on either side by banks of oak trees and bearing a brass plaque with the words: Woodholme School for Boys: Lower and Upper Preparatory.

From where we're sitting we have a great side-view of a sweeping driveway that leads up to a massive sandstone building. The sound of small children shrieking echoes in the distance. There are two playgrounds separated by a wire fence. One contains a climbing frame, a scattering of animal statues in painted metal and a horse-chestnut tree in the corner. The other playground is bigger and clearly for older kids just a tarmac square, though the branches of the horse-chestnut tree hang over it.

'We can't wait around here for very long, Gen, if that's what you're thinking.' Lorcan frowns as he looks at me. 'It's too risky. Some nosey do-gooder will call the police and say we're lurking out here.'

'I don't think we'll have to wait too much longer.'

'And what makes you so sure of that?'

'Bobs back at the shop definitely knows Art, yes?' I say.

'I'd bet my life on it.'

'So he'll warn him and Art will send someone to pick up . . . this child.' I want to say my child but I still can't get my head around the fact that the baby I've been dreaming of for nearly eight years might be a boy, not a girl. It all feels unreal. I force myself to be logical. 'If Art knows we're on to him, he'll act. He'll know he won't be able to get to the school before we do, but he'll want to get the child out of here. That's if the child goes to this school.' I glance at the sign on the wall. 'If he's eight he could be in the lower or upper prep.'

Lorcan nods slowly. 'You think he might send the woman he's with to take him out of school?'

Fury builds inside me. 'If they're in this together I imagine she'll want to come as soon as she can.'

We sit in silence for what feels like a long time. Several women pass us on the pavement. Others pull up in cars. Then a bell rings loud and sharp from inside the school. Seconds later scores of children swarm onto the playground. As their voices fill the air, all the women who haven't already left their cars get out and walk through the school gates. More appear from around the corner, strolling along in pairs and groups, many holding smartly dressed toddlers by the hand.

'The invasion of the yummy mummies,' Lorcan says drily.

'It must be going-home time,' I say, my throat dry.

It couldn't be worse. I'd expected to see a single child being taken out of school early. Now I'm going to have to pick one out of a crowd.

More women pass us, chattering away. They're mostly my age or a bit younger; lots are pushing buggies or prams.

We get out of the car and wander through the school gates. Mothers and nannies and their charges are trickling past. I scan the scene feeling desperate. If my child is here, how will I know? I look for a woman in a hurry . . . someone scared and furtive . . . but everyone around us seems happy and relaxed.

It's hopeless. A new terror fills me. If Art knows I'm here, and this boy is our baby, then Art will move him away from this place, from this school, and I will have to start tracking him down all over again. I think about the mugger and his threat: Stop looking. I have gone against his order. I have kept on searching.

My life and possibly Lorcan's is in danger. But I need to find this child. I need to know if he's mine. I need something concrete that I can take to the police.

I gaze around. More children are emerging from the younger kids' playground. Most are chattering away, several clutching paper hats with streamers that flutter in the breeze. The sun comes out and some of the women shield their eyes from the glare. I stare from woman to woman. From boy to boy. Each one wears a pale blue Woodholme sweatshirt over long navy shorts. They're a homogenous bunch: almost entirely white, with fresh round faces and high-pitched squeals.

More groups flood out through the school gates now. I can't keep track of them all. I fixate on the hair. Most of these children are blond . . . or blondish . . . but Art and I have always had dark hair. Would our son be dark too? I start walking through them, turning as I stalk the gate area, trying to see every face . . . scanning all the women, all the dark-haired kids.

And then I see him. And everything I've ever known shifts and reframes.

He's racing another little boy across the playground, a look of intense determination on his face. His dark hair is cut short round the back and sides, but hangs in a floppy silky fringe low over his forehead. I stare at his face at the dark, serious eyes and at the way his bottom lip is thinner than the top and it's like I'm looking at the photo of my dad as a little boy come to life.

This is, without a doubt, my son.

I stare at him. Lorcan follows my gaze to the little boy. I remember showing him the picture of my dad as a child and wonder if he's noticed the likeness too.

'D'you see it?' I ask, breathless.

'He has Art's colouring,' Lorcan says 'but there's something else too. He looks like you around the mouth, I think.'

'He looks just like my dad.' As I speak the words, the enormity of the moment presses down on me. This is as basic as it gets it's genes, it's blood, it's family.

A young woman goes over to the boy. My boy. She's plumply pretty, with a short, spiky haircut that would suit someone skinny and petite but sits strangely above her round face and rosy, milkmaid cheeks. She's wearing a bright pink tracksuit that is stretched tight over her bum. Is this the woman Art took our baby for?

My mind does the maths in my head. Even if she's a bit older than she looks, this girl couldn't have been more than sixteen when the boy was born. Surely there's no way Art could have been having an affair with someone that young?

I start walking towards the boy. The plump girl is gesticulating wildly at him, clearly trying to draw him away from his game. As I get nearer I can hear her sharp, nasal whine.

'Come on, Daddy said we have to hurry.'

The little boy growls in annoyance, dodging the girl's hand as she lunges to grab him. He sprints away to the point where the playground meets the drive. I keep my eyes on his face. He's grinning now, one eye on the girl as he chats with the little boy next to him. They are pointing to the horse-chestnut tree on the far side of the playground, gearing up for another race.

The grin falls away and the child's mouth sets in a determined line again. As they start running, Lorcan whispers in my ear.

'I'm going to get that girl talking,' he says. 'You speak to the little boy. Find out what you can.'

I nod and head for the racing boys. My son how strange those words sound is putting everything he has into the sprint. Despite the other boy's longer legs, for a few moments he is going faster . . . he's going to win. I will him to. And then he trips and slams into the ground.

The other boy reaches the horse-chestnut tree first and punches the air with a whoop.

'I beat you, Ed, you sucker!'

Ed.

I rush over as he picks himself up off the ground. His knee is grazed red raw.

'Are you all right?' I gasp.

Ed ignores me. His lips are pressed tightly together, like he's trying not to cry. The grim determination on his face has collapsed. For a second, all I can see in his eyes is defeat. And shame. I've seen that look before. A shiver snakes through my entire body as the memory overwhelms me a man pressing his palms against a rough pillar. These stones heal the sick.

It's more than just the set of the features. It's like the ghost of my father has just drifted across the boy's face.

My father. My son.

I glance over my shoulder. Lorcan is talking to the girl who was calling Ed. It doesn't look like she's noticed him fall over.

The other boy runs off and Ed looks up at me.

'Hi.' I squat down so I'm at his eye level, with the horse-chestnut tree behind me. 'You're Ed, aren't you? You're brave not to cry about hurting your knee.'

The boy looks at me with huge, serious, brown eyes. He glances over at the girl who was calling him. She's busy pointing out of the school gates, explaining something to Lorcan.

'I thought you ran very well,' I say. 'You're fast.'

'I'm the fastest in my class.' The way he says it sounds like a fact, not a brag. The same knack of delivery that Art has. My heart beats faster.

'Are you all right?' I say.

The boy sticks his lip out. He's obviously deciding whether it's okay to talk to me. Then he looks around, taking in the other mums and kids and the sunshine. His gaze fixes for a moment on a curling tear in the wire fence that separates the playground we are in from the one next door. I hold my breath, hoping the environment is sufficiently secure for him not to start screaming for help.

Clearly he decides it is. 'I'd have won if I hadn't fallen over,' he says.

'I could see that.' I gulp, desperate for more information. 'So what's your name Ed what?'

The boy stares at me, instantly on his guard. 'I'm not supposed to talk to strangers.'

'Of course.' Out of the corner of my eye I can see that the girl has clocked me. Lorcan's still talking to her, but she's edging towards us. I can hear them both now Lorcan is talking in an English accent, pretending his kid has just started at the school.

'Is that your mummy?' I ask, my palms sweating.

Ed wrinkles his nose. 'No way, that's just Kelly. She looks after me.'

Well, that's something. At least Art's mystery woman isn't a child herself. My mind skips again through the options. There's Sandrine, of course. And Hen, though I can't see how. Charlotte West is older than I would have expected. Or maybe someone Art knows through work, like Siena, his secretary, or Camilla on reception. Or another client's wife.