Obsession: The bestselling psychological thriller with a shocking ending. Amanda Robson

a quick drink,’ I overhear her explaining to yet another person I don’t recognise.

      Rob returns from the bar with a glass of red wine and a pint of Doombar.

      ‘She knows so many people,’ Rob says, his eyes following mine as I watch.

      ‘It’s the choir thing.’

      ‘It’s the church thing.’

      ‘Maybe it’s because she’s nice,’ Rob says.

      ‘Nice is such an ordinary word.’

      ‘There is nothing ordinary about Jenni.’

      ‘Don’t start that again.’

      ‘I didn’t start it in the first place.’

      Saturday morning. I’m in the car with John and Matt. Pippa is out for the day at a friend’s house, doubtless being drowned in pink. Pink-walled bedroom, pink ballet dresses, a selection of dolls all dressed in pink. Suffocation by candyfloss.

      ‘Where are we going, Mummy?’ Matt asks.

      ‘Snakes and Ladders.’

      ‘Why isn’t Daddy coming with us?’

      ‘His turn for a lie-in.’

      ‘What about Jenni and the other Gospels?’ John suggests hopefully.

      Wincing at the use of the word Gospels, the cheesy nickname Jenni has coined for our children – Matthew, Mark, Luke and John, the conjoined products of our NCT friendship.

      ‘I thought we could enjoy some time on our own,’ I reply.

      ‘Please, Mummy. Phone Jenni. You can talk to her while we all play on the slides,’ Matt begs.

      Jenni. Holding my hand and laughing. Jenni. Before she started making cow eyes at Rob. I push the memory away.

      ‘You’ll have to make do with Mummy,’ I snap.

      I signal to pull off the main road, and turn into the car park of the state-of-the-art climbing facility. Brightly coloured plastic slides and climbing nets, all hidden from parental sight by giant yellow plastic walls. It’s simple, and expensive. You pay for your children to go in. They take their shoes off, leave them with you and disappear. You sit and drink coffee. You read a book or a newspaper. They reappear several hours later, hot, sweaty and requiring drinks, but too tired to give you any more trouble for the rest of the day. A perfect way to keep children amused on a Saturday morning. Maximum expense. Minimum effort. My favourite treat for them.

      After I have flashed my credit card, my sons disappear through the yellow and blue plastic doorway that leads to the gargantuan play frame. I buy a large cup of coffee and a shortbread biscuit from the café and set myself up at a table. I plug my earplugs in (small foam ones that I bought at Boots yesterday), spread my newspaper out on the table, and home in on the magazine supplement.

      I must have fallen asleep because the next thing I know, I open my eyes to find John shaking my arm. He is red-faced, blond curls plastered to his head with sweat.

      ‘Can I get you a drink?’ I say dutifully.

      ‘When we’ve found Matt.’

      ‘Found him? I thought he was with you.’

      ‘He was, Mummy, but when I went down the wiggly slide, I thought he was behind me but he never arrived.’

      ‘He’s probably just in another part of the slide complex. Let’s go and ask the staff.’

      Holding John’s hand, I venture through a yellow and blue doorway, into a world where toddlers tumble and twist through nets and tubes, thundering towards me at frightening velocities. But it’s only me that is intimidated, not the toddlers. They are laughing and smiling as their chubby bodies slide and bounce. At the bottom of every tube or net there is a substantial amount of blue matting and a Snakes and Ladders guard; a young adult wearing a canary yellow sweat shirt. I approach the nearest guard, clinging tightly to John’s hand to keep him with me.

      ‘Excuse me,’ I say to him, a boy of about sixteen. A boy with a pulpy face, a rash of spots on his right cheek. ‘I can’t find my other son.’

      ‘What’s he wearing? I’ll look out for him.’

      I hesitate.

      ‘Black jeans and a T-shirt,’ John replies before I can remember.

      ‘And his name?’

      ‘Matthew Burton. Matt for short,’ I reply.

      ‘Tell me a bit more about what he looks like.’

      ‘He looks about five – but he’s only three and a half. And his hair is blond, like his brother’s.’

      ‘That’s me,’ John proudly informs the pimply youth.

      ‘Wait in the café, I’ll go looking for him and bring him to you as soon as possible,’ he replies, a little sharply. He is looking at me critically, but I ignore him.

      By the time he has finished his sentence John has freed himself from my hand and is climbing up a purple net. Before I have returned through the plastic door to the café for another cup of coffee, John is already halfway up the giant play frame.

      Half an hour later, a man wearing a suit and an earpiece is standing in front of me holding John’s hand. Attached to his shirt is a plastic badge telling me that he is the manager of Snakes and Ladders. Only his badge and his earpiece prevent him from looking like a funeral director, so low are his eyes, so dark his grimace.

      ‘I’m sorry to say we can’t find your son Matt on the main play frame,’ he announces.

      My stomach tightens in annoyance.

      ‘He went in. He must be there,’ I reply.

      ‘We’ve checked every camera for twenty-five minutes.’ There is a pause. ‘Is it possible he ran past you and went outside?’

      ‘I wouldn’t have thought he would have done that.’

      ‘Is it possible?’

      ‘I fell asleep. So it’s possible. Unlikely, but possible.’

      ‘We have another play complex outside. Maybe he went there.’

      ‘Why would he do that without telling anyone? He’s never been there before.’

      John starts to cry. ‘I want my baby brother.’

      I lift him into my arms.

      ‘We’ll find him. He can’t have gone far,’ I tell him.

      We follow the manager out of the Snakes and Ladders indoor arena, across the car park towards a large wooden climbing frame built in the shape of a fortress with boardwalk walls. The castle teems with children racing around the walls. I stand next to the manager, clinging on to John who is still crying, and a fist of panic suddenly squeezes me inside. Where is my son? Where has he gone? What’s happened to him? Then almost as soon as I start to panic, in the edge of my vision, like a speck of dust irritating me, something makes me turn to the corner of the climbing frame, and for a split second I think I see a boy of about Matt’s size, with blond curly hair.

      ‘What is it?’ the manager asks. ‘Did you see something?’

      ‘I thought I saw him.’ I shake my head. ‘But maybe I didn’t.’

      And then I see him again. Matt. Matt’s hair. Matt’s red face. Matt’s black jeans and new flashing trainers running down the steps of the castle towards me. I manage to keep calm in front of the manager – who no longer looks funereal – the swarming children, and their over-vigilant parents who are hovering anxiously by the play frame. But as soon as I strap him into his car seat to drive him home I smack him, hard on his cheek. He cries. John starts to cry in sympathy. I drive home with two crying boys who are howling and bellowing, wishing I knew where I’d put my earplugs. As soon as I have