She looked at me, then right through me. She was wearing a t-shirt and knickers. 'I know you're out here,' she yelled, shockingly loud. 'I hear you.'

I pride myself on being able to deal with difficult, angry clients; can't remember a time when calm handling and a cool head didn't defuse a situation. 'Sacha. Look at me,' I said clearly. 'I'm here.'

'I know you're there,' she snarled. As I took a step closer I realised that she was glaring into the distance, listening to a voice that wasn't mine. Her gaze was flickering fast from one side to the other, her head darting like a snake about to strike. 'Where are you? Come on! Show yourself.'

Close behind her, Finn moved among the leaves. Instantly, Sacha's eyes narrowed. She whirled around.

'Got you!' she hissed, and reached out for him.

I ran.

Oh, I ran. Time froze, as though the moment was crystallised, as though it would last forever. And it will last forever. I shall be running down that balcony for the rest of my life, and Sacha will be gripping her brother by his arms; she will be lifting him easily and holding him high in the air. She has the strength of ten men-how can she be so strong? I shall hear the pounding of my feet on the boards. I'll stretch out my hands, and scream.

But I'll always be too late. Finn will fall. He'll plunge headlong, tiny hands clutching at nothing.

So here's the question: what if your own daughter is a monster? Do you point and shout? She's an addict, a dealer, a thief. She's the devil who attacked your little son. I feel as though I'm cradling a ticking bomb.

Honesty isn't always the best policy, never mind what my mother says. Kit has a right to know what really happened to Finn, but I can't tell him. I really, truly can't. I feel as though I'll never love Sacha again or even look her in the eye. How can I expect him to? No, he'll leave me. He'll leave, and take the twins with him because they aren't safe near Sacha. The idea terrifies me because I can't bear to imagine life without Kit and my little boys. It would hardly be worth living.

What's more, if I blow the whistle those nice policemen will go straight out and arrest Sacha. They'll take her away. What will they charge her with-grievous bodily harm, attempted murder? Oh, and dealing in drugs, for good measure. Her life will be over, and so will Finn's and Charlie's. The boys are the real victims in all of this; the only ones who are completely innocent.

I'm alone, clutching that ticking bomb, and I mustn't drop it. If I drop it my family will be blown apart. If I can hold on, we all have the chance of a normal life.

So I tell Kit my story: how I sat on the sofa in the dark, waiting for him to come home. I describe how Finn wandered out of his door and climbed onto the rail as quick as a monkey.

'I ran,' I whisper. 'I ran, and I screamed at him. But he wouldn't wake up, it was like a nightmare. He just . . . toppled over the edge.' I can see it all, feel it all; I shudder at the monstrous thud. 'It's my fault. I wasn't quick enough.'

Kit covers my hand with his. 'It's not your fault.'

I hear voices, and glimpse Neil Sutherland's corrugated-iron hair. He's brought some sidekicks. They're in a huddle with a senior nurse.

I move closer to Kit. 'They think one of us did it on purpose.'

'They think what?'

'I've had a social worker trying to get a confession out of me. D'you remember when Finn came off his bike on New Year's Day?'

'Did he?' Kit's brow furrows. 'So he did.'

'It turns out his wrist was broken. It's healed now, but it showed up on an X-ray. And there are some bruises on his arm . . . they look like finger marks. So they've been getting their knickers in a twist. I mean, for G.o.d's sake, Kit! He's covered in bruises.'

'They think we've been abusing Finny?' Kit looks incredulous.

'They know you flew in yesterday, but I fibbed about it at first. I didn't want any awkward questions about why you came home and left again.'

He's on his feet, shock channelled into anger. 'Who do I speak to? Bring it on!'

'Calm down. You're being watched.'

'I don't give a f.u.c.k if I'm being watched.'

I put my arms around him, murmuring into his ear, 'They think one of us lost our rag and hurt Finn. So settle down, and stop behaving like a man who loses his rag easily.'

When Sutherland and his wing-men arrive, Kit collars them. 'Can you tell me what's going on here?'

'You're Dad, are you?' Sutherland is obviously used to agitated parents. He introduces himself, leans on the edge of a little basin and explains everything again. 'Finn arrived early this morning in a life-threatening condition-the helicopter team did a great job in keeping him stable until he got to us. He had a head injury and a ruptured spleen, both of which needed urgent surgical intervention. From an orthopaedic point of view, he got away with a fractured radius and ulna-least of his problems. We've just been discussing his progress and we're pleased, but he's still a very poorly boy.'

Kit has simmered down. After all, these people undoubtedly saved Finn's life. 'Thank you,' he says fervently. 'Thank you for what you did. Will he live normally without his spleen?'

'I'd say so. At the moment, I'm more concerned about the head injury.'

'And what's this about it not being an accident?'

Sutherland is unruffled. 'Whenever a child is injured we have to consider whether parenting fell short in some way. And there are features about Finn's presentation that raised concerns, so we consulted with the paediatric social worker.'

Kit points at me. 'Martha's never laid a finger on any of our kids, and she never would! Or am I chief suspect? If so, I checked into a motel in Westsh.o.r.e at about midnight last night. The bloke will remember me all right because he was in his dressing-gown.'

Sutherland's pager begins to bleep. 'It really would be best if you discussed this with Mrs Pohatu. Make contact with her tomorrow. Excuse me-I'm being paged.' And he is gone, marching through the swing doors with his squad.

'Why us?' Kit looks bewildered. 'What about all the truly abused kids who fall through the net? They get hurt time after time, live in abject misery, but n.o.body sounds the alarm and the poor little blighters wind up dead.'

We sit with Finn all evening. This is a ward on a knife edge, continually battling with death. n.o.body relaxes, ever. And our Finn is here. Kit wants to hear every detail, yet again: the fall, the helicopter, my long vigil. He needs to understand exactly what each specialist has said. We talk around and around, promising one another with brittle airiness that Finn will be fine.

Finn doesn't look fine. There's no flicker, no sign that he is still inside the battered mannequin. He lies inert, plugged into his bank of machines.

Eventually, Kit asks about Sacha. I give him the barest facts: she's relapsed, given away her car, come home in a dreadful state.

He's holding Finn's hand between his own. 'Let's focus on this little guy. I can't think about anything else. Jesus, what else matters? Once this is all over we can worry about Sacha. We'll ask for professional help, do whatever it takes.'

I am only too happy to go along with his plan. I'm not capable of making life-changing decisions, either. My care, my will, my every thought and instinct is centred in Finn's survival. Nothing else exists.

'It's going to be all right,' says Kit, as though to rea.s.sure himself. 'He's a fighter.'

I close my eyes. A demon s.n.a.t.c.hes up Finn's puny body-got you!-and hurls him out into the darkness. I'll never forgive her.

It's after ten when the senior nurse approaches us. 'I'd suggest you both go home and get some sleep,' she says firmly. 'Finn is stable. I promise we'll phone if there's any change at all.'

I'm aghast. 'Can't at least one of us stay?'

'Yes, you can. We won't throw you out. But look, you really should rest because you both look terrible. I know you were up all last night, Martha, and you-' she raises her eyebrows at Kit-'have only just flown in from Europe! You two have to look after yourselves. This little boy's recovery is going to be a long haul.'

Reluctantly, we obey. As we kiss Finn goodnight, Kit pulls something out of his pocket and lays it on the bedside cabinet.

'Charlie sent your Game Boy, friend.'

Thirty-seven.

We leave Kit's car at the hospital and drive home together. Sacha runs out to meet us, tearing my door open.

'How is he?' She's breathing fast. I can hear the terror and love in her voice, but I can't bring myself to look into her eyes. I turn away, pretending to search for something on the back seat.

'He's all right,' I say shortly. 'Actually, no, he's not all right. He has a plate in his skull, no spleen and a broken arm. He could still die.' I want to shake her. I want to thrust my face close to hers and scream blue murder. You did this. You did this.

She bursts into stormy tears. Kit looks at me in astonishment. 'Mum's pretty stressed,' he soothes, walking around the car to comfort his stepdaughter. 'Finny's doing well. He'll be playing football again before you know it.'

Tama and Bianka stand waiting for us at the kitchen door. 'Mum says she's thinking of you.' Bianka hugs me. 'If you want to stay at our place, save you driving so far . . . she says just to turn up.'

I'm touched by this message from one mother to another. We sit around the kitchen table, nursing mugs of tea. Charlie has fallen asleep in front of Mary Poppins and been carried up to bed. They tell me Ira was here earlier, but he's gone home.

'I can't believe it,' Sacha keeps muttering. 'Right outside my door.' She doesn't seem to be able to move on from this idea. She repeats it over and over, no matter what conversation the rest of us are having.

'Hey.' Kit taps her forearm, making her look at him. 'Listen, young lady. It wasn't your fault. Just get that into your head. Isn't that right, Martha?'

When Tama leaves, the rest of us begin to turn in. Bianka has already made up a mattress in Sacha's room, though I feel my daughter doesn't deserve such devotion. As I pa.s.s their door, Sacha calls out to me. My mind is fouled by an image of a fiend with devil's eyes, reaching for a tiny boy. It's like a film clip in my mind. It keeps replaying, over and over again.

'Where's Bianka?' I ask, looking around. The room has that familiar, ugly smell.

'Getting stuff from her car.'

'I'm going to bed,' I say, ma.s.saging my face. 'Haven't had any proper sleep for days, and I want to be up and off early tomorrow.'

She's sitting on the bed, picking at her arm. Her pillows have no covers, and the sheet lies in a heap on the floor. 'Last night was like a horror film.'

'You're right there.'

'I saw . . . I've never been so scared. I saw people.'

'People?'

'Crawling along the floor, whispering, like sort of human snakes. They had these weird eyes that gleamed. It was the freakiest night of my life.'

'Mine too.'

'And this morning-I just about died when I heard about Finn! It's like . . . nightmare meets reality. No more, Mum. No more. I never want to go through that again.' Sacha looks sickened. 'It was so dark.'

'We'll talk about it later.'

'I'm going to feel completely s.h.i.t while I come off it. I feel completely s.h.i.t right now. It's calling me already. It's calling me. Why can't I block my ears?'

'You tell me, Sacha. Why can't you?' I head for the door.

'I'm coming to see Finn tomorrow,' she says.

I stop. Hatred rises in my throat. I'm about to tell her that she can't see Finn ever again because she's a devil in human form, but when I turn around she's hunched on the edge of her bed, childishly round-eyed, squinting up at me with a mix of anxiety and trust. I know that look so very well, and I see no devil.

I wake at four. My mind is flitting like a fantail, never stopping, never resting. Kit sleeps beside me. He believed my story without question. He believed my lies. I can't bear it.

By four fifteen I've made a decision, once and for all. I'm going to tell the truth. Kit, Sacha, Finn and Charlie all have to know-how could I even think of covering up? I'll tell them, and they must deal with the appalling reality. Then, of course, we will go back to England.

By four thirty I've changed my mind. No. No, there is only misery down that road. I must keep my secret. Sacha is dismayed by her psychosis; she'll stay clean this time. If I can carry my bomb without dropping it, our family might-just might-be happy again. I even begin to hope we might stay here, in our own paradise.

By five I've changed my mind twice more. I can't think straight. I roll out of bed and pull on jeans, two sweaters and a pair of Kit's socks before padding down to the kitchen. m.u.f.fin is in her basket. When I lean to pat her, she stretches luxuriously and her tail flaps on the floor.

'Life's a b.i.t.c.h, m.u.f.fin,' I say. 'No offence.'

I try to phone Dad but he isn't in. Maybe he's away. I remember he said something about chairing a Rudolf Steiner conference sometime soon. In black loneliness, I try Lou's number. I get her answer phone, and don't leave a message.

Finally I stoke the stove and pull up a chair. Then I sit fretting, letting the warmth sink into my bones while m.u.f.fin clambers stiffly out of her basket and rests her head on my knee, eyes hidden by her schoolgirl fringe. When I hear the kitchen door inch open, I almost jump out of my skin.

'It's okay.' Bianka's low, smooth voice. 'Only me.'

'Jeepers, Bianka! I don't know how many more night-time horrors I can take.'

'Sorry.' The serene figure drags up a chair next to mine and sits down, wearing bed socks and a hoodie over her pyjamas. She's striking even in grungy nightclothes and without the blackberry lipstick. Her cheekbones are fine beneath the pale skin, her hair a dark gold-though a little frizzy this morning.

I squeeze her shoulder and get up to fill the kettle.

'Sacha kept me awake,' she says. 'Muttering and grinding her teeth.'

'Bless you for coming here yesterday. How did you know we were in trouble?'

She strokes m.u.f.fin's nose. 'Sacha hadn't spoken to me for weeks. Then yesterday morning-six o'clock?-I got this really weird call. She was in a state, going on about Finn and how these beings had come down from the hills to get her. It's meth psychosis, you know? I read about a guy who looked at trees, familiar trees that he saw every day, and thought they were people.' Bianka sits very still, her fingers resting on m.u.f.fin's ears. 'She said these creatures had come creeping along the balcony and into her room, whispering to her. She didn't remember much, but she remembered the fear. She was kind of delirious. When she woke up she wasn't in bed.'

'Where was she?'

'Sitting in her cupboard! She's no idea how she got there.' Bianka gets up and stands with her back to the stove, watching me. 'You know, it seems . . .'

I'm looking for teabags. 'Mm?'

There's a melancholy smile on the cupid's-bow lips. 'Well, you know, it just kind of strikes me as a bit of a coincidence. You've got Sacha, who's freaking about things on the balcony, and in the very same night you've got poor little Finn tumbling off it.' I freeze with my hand in the teabag jar. 'And then I noticed . . . I'm sorry, Martha . . . I noticed that her balcony door wasn't quite shut.'

I close my eyes for several seconds. Finally I make tea in two mugs, add milk and give one to Bianka. 'What would you do, if you were me?'

'I'd tell her. I wouldn't leave her with a h.e.l.lish half-memory. She needs to face it head-on, or she'll relapse again.'

'She says she's finished with it.'

'Ever heard that before?'

I'm silenced.