I feel so twisted up inside myself. How could I have failed to suspect her? I’d thought through the possibilities of it being a thousand people, but most of them had been strangers.

Harriet Watson had left Evie alone in the classroom that night, neglecting her for a length of time that was long enough for my daughter to be abducted. At least, that was what I’d believed, and it was what everyone else had believed, too. Most theories – and everyone was an expert – had run along similar lines.

All alone, Evie must have wandered outside, looking for me, and been whisked away into oblivion by an Eastern European trafficking gang, or a paedophile living nearby.

I haven’t emerged from the tragedy as an innocent party, not by a long shot.

I am the ‘uncaring bitch’ who arrived late to school.

I am the ‘drugged-up excuse for a mother’ who relied on sedatives to get through her crippling grief.

I am the ‘inadequate failure’ of a woman who must not be trusted or believed under any circumstances.

But it seems so obvious, now.

Since Evie had gone, Harriet Watson has attempted to contact me many times. The police warned her off at first. For a couple of weeks she was actually a suspect in Evie’s abduction. But in the end, the police were satisfied that she was merely negligent. Everyone agreed she should never have left a five-year-old child unattended in a classroom, no matter how late a parent was to collect her.

Mr Bryce, the school caretaker, gave evidence stating that when he checked the classroom doors, Rowan Class was unlocked, including the French doors leading directly out into the unsecured grounds.

To all intents and purposes, it looked like my Evie had just walked outside looking for me and was picked up by an opportunist.

The struggling school budget did not support a CCTV system and a local football match had ensured that most people living nearby were away from the surrounding homes, supporting their local team.

The local media – which quickly gravitated to national media, and then back again, when the big newspapers lost interest – condemned Harriet Watson and specifically St Saviour’s School.

But they saved their real vitriol for me. The single mother who’d been unacceptably late that day.

After the ‘Find Evie’ publicity had started to die down, surprisingly quickly, Harriet Watson began writing me letters. Crazy, rambling, handwritten letters where she would start by condemning my parenting skills, or lack of them, and then graduate, over a few pages, to offering me her friendship and her self-proclaimed counselling skills.

In one letter, she told me she had already begun to counsel Evie on the loss of her father, encouraging her to discuss her feelings in the group. This was apparently going to ‘prepare her for her future’ and ‘help her grow a thick skin for when she moved up to the local comprehensive school’.

By this time, Watson had been sacked from her job by the school governors, but through DI Manvers I expressed my utmost concern at the regular and widely accepted practice of teaching assistants working with isolated groups of children.

Of course, most teaching assistants are not like Harriet Watson, but still, the opportunity was afforded to her and she gladly took it.

After I received that letter I vomited for a full day. I couldn’t eat for a week. I hated myself, loathed myself. I wanted to die. I couldn’t stop thinking about all those times Evie had told me how she hated school, how Miss Watson made her talk in the group when she didn’t want to. She had felt uncomfortable and came to the person she trusted most in the world. Me. And I doubted her, swept her concerns aside.

Mum’s gut feelings about Harriet Watson had been right all along.

I ignored all Harriet’s letters from that point forward. I read them, I couldn’t help myself, but I never replied and eventually they came less frequently and finally they stopped altogether.

‘She’s harmless enough but mad as a box of frogs.’ This had been DI Manver’s expert but unofficial opinion. ‘And after meeting her mother, I’d say I know exactly where she gets it from.’

But she wasn’t harmless.

She hurt Evie, knocked her confidence. Humiliated her in front of her peers, forced her to speak about the most personal things, such as her daddy’s death. St Saviour’s gave her the opportunity and power to wield over very young children who were not equipped to fight back. And for that reason, I can never forgive the school.

I hated Harriet Watson for what she did. She let Evie down.

But I’d seen a counsellor for eighteen months after Evie’s abduction and she helped me see that I was accountable too. I learned how to forgive myself and to forgive Harriet Watson, too.

But I was naïve. New evidence has now come to light that someone else was involved and I am completely convinced it was Harriet Watson. It could only be her.

My rage and hatred has been born anew.

I am certain that, between them, Harriet Watson and Joanne Deacon know what happened to Evie.

I just don’t know how or why they did it, yet.

I decided from the outset that I would not be involving DI Manvers in any of my planned actions. He and his team have already let Harriet Watson off the hook and have obviously completely failed to properly investigate Joanne Deacon.

I wait until it’s dark outside. I dress in jeans and a charcoal-grey duffle coat with hat, scarf and gloves. I pull the hat down low over my forehead and leave the house. I turn back to the window to see Mum peering out, her face etched with concern.

It’s going to kill her, what happened to Evie. If we can’t find her, she will just continue to get frailer and then she’ll just let go of life. We have never discussed what happened; it’s odd. You don’t always know how you’re going to react to a sudden tragedy breaking your life into little pieces.

Me and Mum will discuss whether to have egg or beans on toast for tea, or occasionally what is happening in politics, but we never talk about Evie and whether she is alive or dead. It’s how we get through the horror of each long, drawn-out day.

I tell Mum, ‘I need a walk to clear my head.’

But when I leave the house, I can tell she doesn’t believe a word of it.

It has been a lonely three years but that’s the way I wanted it. I couldn’t handle people. After Evie disappeared, both Dale and Bryony sent cards and letters, and Dale had turned up with flowers on more than one occasion, but I had Mum send him away. I just couldn’t do it.

I couldn’t see him.

The only person I kept in touch with, and who has been a true support to me, is Tara. We never get together or meet up, we just chat on the phone. Tara, for all her own problems – her MS has grown steadily worse over the years – understands my need to withdraw and be alone. She has retreated herself since Rob died and because of her illness.

Apparently, Joanne Deacon was so upset by what happened that she immediately resigned from Gregory’s and moved out of the area. And now she is lying in a hospital bed, just a shell, a husk. We have no way of accessing further information about what she did with Evie or why she did it.

But Harriet Watson knows. I just feel it.

It takes me half an hour to walk to a bus stop far enough away that I feel a little more anonymous. Frost covers the pavement like a dusting of shimmering icing sugar. Evie used to love it when it was like this. She’d wake up and look out of her bedroom curtains, declaring, ‘Mummy, Jack Frost has been!’

For a few blissful seconds I can almost imagine she’s with me right now. The warmth of her little hand in mine, the constant chatter and curiosity for the world around her.

My eyes prickle and the feeling quickly crumbles, leaving behind only icy fingers of grief that claw at my heart.

I’ve always felt . . . known . . . that Evie is still alive.

But what have they done with her?

And what possible reason could two women, both of whom knew me, have for taking my daughter?

After working through a hundred scenarios and what-ifs in my head during the short bus journey, it is all so unexpectedly simple.

I knock on the door of the house and Harriet Watson answers.

I barely recognise her. She doesn’t stand but stoops, bent over like the letter C, her shoulders rounded, as if something on the inside has pulled tighter and tighter until she has given in.

Her brown, curly hair has turned white. She still wears spectacles but seems almost blind, peering closely in order to see my features.

‘Toni?’ she whispers.

I don’t answer and she stands aside, watching me, in awe that I am actually here, in front of her, after all this time.

When I get inside the house, I screw up my nose. The air is fetid.

‘It’s the drains,’ she says slowly. ‘I’m used to it now.’

Nobody could get used to that smell, it’s impossible. She must have dead rats blocking the sewers, waste must be backing up. It can’t be healthy, breathing it in, but that’s the least of my concerns. I’m certainly not here to advise her on hygiene.

‘Please, come through,’ she says, like I’ve arrived for a tea party.

We move into the lounge. The room is dark and smells fusty. The carpet looks as if it hasn’t been vacuumed for months.

She offers me tea and I decline.

‘I came to tell you that I know,’ I say, watching her. ‘I know everything.’

‘You know everything about what, Toni?’

‘I know you helped Joanne Deacon. You helped her take Evie away from me.’

‘I – I didn’t know who she was,’ she stammers. ‘Until I saw the newspaper, I didn’t know she’d lied to me all that time. She asked me lots of questions, but I swear, I didn’t know the reason why.’

‘I just want to know where she is. Harriet, where is Evie?’

‘You don’t understand,’ she says. ‘I didn’t help her take Evie, I just told her things, provided answers to questions she asked.’

‘Questions like what?’

‘I can’t remember. I’m so sorry about what happened but I didn’t do anything on purpose. I want to be your friend, I want your forgiveness.’

She’s babbling, confused. Her eyes dart around as she speaks to me and she keeps looking at the ceiling. It’s unnerving, but I have to remind myself I am here to find Evie and that I have to play a clever game.

And I have to remember that Harriet Watson has managed to fool the police once before. The worst thing I can do is underestimate her.

‘Could I use your bathroom?’ I say, standing up.

She jumps out of her own seat. ‘No, I’m afraid you can’t because of the drains, you see.’

‘Is it OK if I just get a glass of water, then?’ I change tack.

‘Of course, I’ll get you one.’

I follow her into the kitchen. We pass the steep, dark stairs on the right and I swear the smell is worse. I hold a tissue up to my face.

The kitchen is tidy but old and the cupboards are falling to pieces. There is a faint smell of damp. She runs the tap and fills a glass. While her back is turned, I slip a key that is hanging from a hook by the table into my pocket. It looks like a back-door key.

She turns and hands me the glass.

‘I’m sorry for your loss, Toni, I am. I don’t know—’

I don’t answer, I just walk out of the kitchen. She rushes in front of me, shepherding me past the stinking stairs.

‘Do you think we could talk?’ she says, her eyes glistening. ‘I’m so sorry for everything. I liked Evie, she was my favourite.’

I look at her and I think about the kitchen knife I slipped into my bag as insurance. But it’s too soon. If I find out the worst about Evie, then someone is going to pay. I don’t care what they do to me after that, I’ll only want to die myself if I find out she’s gone.

The only thing keeping me going is the feeling I am getting closer to finding Evie. The police seem to be retracing their steps, regurgitating old investigations that haven’t led anywhere.

But maybe, just maybe, a different tack could work . . .

‘I’ll give you some time to think about things, write down what Joanne Deacon asked you. Try to remember everything you can. And I’ll be back tomorrow evening to talk. It’s the only way we can ever become friends again.’

‘Thank you, Toni,’ she says in the horribly vacant manner she now has. ‘I will have a good think.’

I leave the house and walk up the street. When she can no longer see me from the window, I stand for a moment, leaning on a gate for support, gasping in fresh air.

She’s hiding something.

Something terrible has happened in that house and I am going to find out what.