Carly comes and stands beside me, rubbing at her wrists and rolling her shoulders. I should ask her if she’s okay, but I find myself unable to speak. I’m still in shock at the thought of what Dr Fisher is about to reveal.

‘Shall I take Harry downstairs?’ Ben asks, walking over to where the little boy has pressed himself into his father’s body. ‘Harry? Shall we go and play downstairs? Want to show me your room?’

‘I don’t want to go!’ Harry cries. ‘I want to stay with Daddy.’

‘Did I hear you say you like trains?’ Ben asks. ‘Have you got any good ones you can show me?’

‘Show him your trains, Harry,’ Fisher grunts, peeling his son off his chest.

‘I don’t want to go,’ Harry wails.

‘Harry,’ Fisher says, his voice stern despite its new hoarseness.

Harry stands, his cheeks tear-stained, his lower lip trembling, but he lets Ben take his hand.

‘Come on, Carly,’ Ben says, turning back to her. ‘You too.’

‘I’m staying to hear this,’ she replies.

‘No, you’re not. Come on,’ Ben insists.

‘No way. I’m not going anywh—’

‘Please, Carly,’ I say. ‘Our deal still stands, but this conversation is between me, Scott and Dr Fisher. Okay?’

She scowls, but does as I ask and goes to join Ben and Harry.

As their footsteps recede, Fisher, still huddled on the floor, begins to tremble. Tears stream down his cheeks. ‘My God,’ he murmurs. ‘What have I done?’

I stare at him in silence, wondering what can be so bad that he’s been reduced to this snivelling wreck of a man, not daring to imagine what he’s about to tell us. But at the same time, I’m almost sure I know.

‘Maybe you’d better start at the beginning,’ I say at last, my voice not sounding like my own. I kneel opposite him, not taking my eyes from his face.

Scott remains on his feet, arms crossed over his chest, still simmering with rage.

‘I… I did something terrible,’ Fisher says. ‘Beyond terrible.’

‘Tell me,’ I say.

‘All right,’ he says quietly. ‘All right.’ He takes a breath and stares up at the ceiling for a moment, briefly clenching his fists. ‘You already know I’m an obstetrician. And yes, I used to practise at the Balmoral Clinic.’ His voice is croaky, barely more than a whisper after Scott nearly strangled him. His eyes are bloodshot and his hands quiver so much he places them between his knees to still them. ‘The night you gave birth, your consultant, Max Friedland, was taken ill and I was called in to cover for him. What you may not know is that my own wife, Liz, also went into labour that night. She was in the suite next to yours.’

I’m listening to him with a kind of fascinated dread, barely breathing.

Fisher’s eyes glaze as he remembers. ‘You were already in good hands with your midwife when I arrived, so I concentrated on looking after Liz. Naturally, I wanted to be with my wife during the birth of our first child, but as the clinic was short-staffed and your delivery seemed straightforward, I was happy to cover. I told your midwife that I’d come to you immediately if you got into any difficulty, but she assured me that things were progressing well.

‘But then…’ He looks from me to Scott, finally lowering his gaze back down to his knees. ‘But then, my own child got into difficulties. The umbilical cord was wrapped around the neck, cutting off blood flow and oxygen. I would normally have a midwife in the room with me, but I was overconfident – I thought I had the situation under control.’ His voice breaks and he clears his throat. ‘I tried everything I could to save her, but I panicked. I’m usually calm, professional. I deliver hundreds of healthy children every year, but this was my child, my wife. The child we’d been trying for ten years to conceive. I… I couldn’t save my own baby. She died. My child died. I couldn’t save her. It was my fault.’

‘She?’ Scott questions immediately. ‘Her?’

‘I made a decision,’ Fisher says. ‘A split-second decision that’s haunted me ever since. You have to believe me, I never planned for it to happen. I wasn’t thinking clearly. I didn’t know how to tell Liz our baby was gone.’

My heart beats in time with his words. A slow marching drum, getting faster.

Fisher turns to me. ‘You had already given birth to one healthy twin. The next one was coming, and that’s when I did it.’

I’m shaking now. My whole body, top-to-toe, my teeth chattering. I know what he’s going to say, but I don’t want to hear it. How will I bear it?

‘Lily was my daughter,’ Fisher says. ‘Mine and Liz’s. But she died a few moments after birth and I was grieving. I don’t think I was in my right mind.’

‘Lily was yours?’ I whisper, a chill sweeping through me.

But Fisher doesn’t reply. He’s intent on his confession. ‘Scott, you were on your phone, texting family members to say you had a son. I told you that mobiles interfered with the hospital equipment and sent you out of the room. Told you to go to the parents’ lounge. I said you had about twenty minutes before your next child came along. I lied.’

He turns back to me. ‘Just before your second child was born, I sent the midwife to check on another woman in labour. You were still woozy from the birth and from the effects of the pain relief. In a moment of utter madness, I swapped them. I swapped my dead child for your living one.’ He pulls at his cheeks, unable to look at me or Scott, his gaze fixed on some distant spot.

‘Harry… he was Sam’s brother,’ Fisher says. ‘He was your second child. He is your second child. I’ve done a terrible thing, I know. I have no excuses. At the time, I told myself that you already had one healthy child. I told myself I did it for Liz, to save her from grief. It would have destroyed her… I am so very, very sorry.’

‘To save her from grief?’ I murmur almost to myself. ‘But what about my grief? What about that?’ He’s telling me he’s sorry. He did this heinous thing and he’s apologising like he took the last slice of cake, or scratched my car, or accidentally bumped me with his trolley in the supermarket. ‘You can’t just apologise for this,’ I spit. ‘You can’t make excuses and apologise for taking my living, breathing baby and swapping him for your dead daughter.’

Fisher is still speaking. Saying the words over and over again. ‘I’m sorry. I’m so, so sorry.’

‘Stop it!’ I cry. ‘Just stop saying sorry. Stop it!’

He closes his mouth for a moment before carrying on with his explanation, taking my life apart with his words. ‘My wife never knew,’ he says quickly. ‘She thought Harry was ours. She loved him like he was our own. So did I. I buried the truth deep, but the truth has sharp edges. It cut me up inside. Every day.’

I want to scream at him that I know exactly how those sharp edges feel. But I will myself to stay quiet. To listen to the rest. His confession is spewing out of his mouth now like an airborne virus, infecting us all.

‘When my wife was diagnosed with terminal cancer, something came over me. An epiphany. I thought, if I don’t tell her about Harry now, I’ll never have the chance. And so I confessed. I told her everything I’d done. She was devastated. Shocked. Disgusted. She had every right to be. She died a broken woman. I did that to her. All I ever wanted was to be a doctor. To help people. But instead…’ He trails off. Buries his face in his hands.

The absolute knowledge of the truth takes the strength from my body, and I lower my head to the wooden floor, curl up and grip my knees, the truth gradually sinking in like poison from a syringe. I have no words now, only tears. My nostrils fill with the bitter odour of realisation. Of loss. Of everything that has been stripped from me. The grief for a dead daughter who was never mine to grieve for. The devastation after Sam died. Being a mother with no children to care for. All of it. All of it too much to bear, knowing that half of it need not have been borne in the first place.

And yet, didn’t I know this even before now? Since that day Harry showed up in my kitchen, those brown curls so familiar, his eyes twin reflections of a lost child.

I knew. Deep down, I knew.

It’s what’s been driving me these past days. Pushing me on despite the risks. That primal knowledge burnt deep into my core: a mother’s knowledge.

‘I’m sorry,’ Fisher repeats on a loop through his sobs. ‘I am so, so sorry.’

A roar jerks me from my frozen position on the floor as Scott charges at Fisher, grabs him by his jumper and yanks him to his feet. I crawl to my knees and watch as he punches Fisher in the face, splitting his lip, sending droplets of blood spraying over him. The doctor’s hands come up too late to protect himself. He doesn’t even attempt to fight back. Just cowers and takes it.

‘I’ll kill you!’ Scott cries, pulling back his fist once more and smashing it into Fisher’s jaw. ‘I’ll fucking kill you, you worthless piece of shit.’

He really is going to end up killing him. ‘Scott!’ I cry. ‘Please, Scott, stop.’

‘He’s ruined our lives, Tess!’ Scott says, letting another punch fly. ‘He took everything from us. Everything.’ His next punch is just as vicious. And the next and the next. ‘He deserves to die for what he did.’

‘Scott!’ I yell. ‘Please! Stop! Think of Harry!’

He must have heeded me, for his next punch is a little less brutal. The one after that, not a punch at all. He finally turns away from Fisher, the man’s face a pulpy mess of blood, tears and snot. Scott’s own face is ashen with grief. I imagine that same grief etched across my features too.

I hold out my arms and Scott staggers into them. We hold each other so tightly that it hurts. Physical pain to balance the other hurt. Fresh bruises so deep and raw that I can’t imagine they will ever fade.

But then it sinks in: Harry is my son. He’s alive. He is here in this house.

And I am his mother.