When I started clearing out the house, I left Anna’s room until last. I’d kept it exactly the same as it was when she still lived there. I noticed some soot around the bottom of the fireplace, which was strange given it hadn’t been used for years, not since she left.

I got my cleaning kit out, and reached up inside the chimney to brush away the grime that had gathered. That’s when a dirty, singed, torn-up letter fell down into the grate. I stared at it for a while, before picking up the pieces of paper covered in Anna’s familiar handwriting. She’d obviously tried to burn them, but they had got sucked up into the flue instead. I knelt down on her bedroom floor and arranged the pieces like a puzzle.

It was a suicide note.

I don’t know how many times I read it, but day turned into night outside the window, and the thoughts inside my mind were just as dark.

She described the terrible things that had happened on the night of her sixteenth birthday, and I felt sick with disgust and mad with rage all at once. I read about the drugs Helen Wang had given her, the men Rachel Hopkins tried to make her have sex with, and how Zoe Harper mutilated our cat as a warning not to tell anyone.

It was a long time ago, but I remembered that night.

We rarely had guests, but I agreed to leave Anna alone with those girls from St Hilary’s, thinking that they were her friends. She was so excited that I couldn’t say no. I watched her spend every evening for a week making friendship bracelets for each of them, and even gave her the red-and-white thread from my sewing basket.

I still had the photo of them all together that night. Rachel gave me a copy a couple of weeks after the party, when I was cleaning her mother’s house. She asked me to give it to Anna. I knew that they’d had some sort of falling out – having been inseparable, they hadn’t seen each other at all – but I did give it to her. I found the picture in the bin the next day. I’ve always had a habit of holding on to things – birthday cards, diaries, photos – and I was glad I held on to that one.

I knew who they all were once I found that picture.

And I knew where they lived; I’d cleaned all their houses.

I might have retired, but I still had the keys, and people rarely change their locks. I finally knew the real reason why my Anna left Blackdown. It was because of them, not me.

They had to pay for that.

And they weren’t the only ones.

Jack left Anna when their little girl died, and I hated him for it. I hated him even more when I followed Rachel Hopkins from the station and saw the two of them fucking in his car. I decided there and then that, despite all the kindness he had shown me, he had to be punished for leaving my little girl and sleeping with that whore.

I fully intended to pin all the murders on him after that. I even borrowed his Timberland boots to wear in the woods. They were too big of course, but nothing a little cotton wool in the toes couldn’t fix, plus it saved getting my own shoes dirty. I started planting evidence in his car and home, and followed him whenever I could. Shortcuts rarely lead to success, but knowing the woods so well made it easy for me to get from one part of the village to another, quickly and undetected.

But then I saw them together again – Jack and Anna – and I knew there was something still there between them. They just needed a bit of help to find their way back to each other, that was all.

When I let myself into Anna’s hotel bedroom – I cleaned that place for years – she looked like a little girl, fast asleep in her bed. It made me feel sad to see her drinking so much, but I understood why. Alcohol was always my drug of choice too. I tucked her in just like I used to, tidied away her rubbish, and put a bottle of water by her bed. It felt so good to take care of her, even if she didn’t know I was there. She reminded me of a bird with a broken wing. I wanted to fix her, and I knew that if my plan worked it would be good for Anna’s career too, as well as her personal life.

Catherine Kelly was the only one of those girls who had left town. When I let myself into her parents’ old house in the woods, looking for clues about where she might be, it was a shock to see a newsreader I recognised in the family photos. The same one who stole Anna’s job.

Killing Rachel brought my daughter home to me.

Killing Helen and Zoe helped me to keep her close.

Killing Cat Jones meant Anna could get her job back on the One O’Clock News, and I would be able to watch my little girl on TV every lunchtime again.

Anna called me on her birthday this year in floods of tears, because she had lost her presenting job. I hardly said a word, and I think she thought I didn’t understand. But I did. And it made me so happy that I was the one she called. For the first time in years she needed my help, and I was not going to let her down again. That’s when I understood that by punishing the people who hurt her in the past, I could give her a happier future. I had to kill them all. I did it for her.

Cat Jones came straight to Blackdown when I asked her to. Admittedly she thought the text I sent was from her husband. I stole Richard’s mobile from his unlocked car when he and Anna were filming in the woods. Then I used his phone to contact his wife. The message was simple enough:

I know what you did with those men in the woods twenty years ago. I’ve seen the photos, and I fear everyone else at the BBC might see them soon too. If you want to save our marriage, bring the children to your parents’ house tonight so we can talk.

I ignored all the desperate texts she sent him, the calls and voicemails. Sure enough, a couple of hours later she arrived at the old house in the woods, with a worried expression on her pretty face and two beautiful little girls by her side.

The rest was easy. When Cat put the children to bed, I took them. I would never have hurt them, but she had no way of knowing that. When she realised they were gone, I listened while she turned the place upside down searching for her girls. She screamed her husband’s name the entire time, as though he had stolen them. It was only when she reached the main bedroom that she was quiet. I’d left some old photos and a note:

Richard isn’t coming and I’ve taken your children. He doesn’t really know what you did twenty years ago and he doesn’t need to. Neither do they – as long as you do the right thing. The pictures on the bed will be destroyed and your girls will be returned to your husband, all you have to do is kill yourself using the school tie hanging from the beam in the ceiling. If you call the police, if you call anyone, your children will not be found until it is too late. The longer you take to do as I ask, the longer they will be in danger. Whatever happens, you’ll never see them again, but if you kill yourself you have my word that they will live.

She took out her phone but it didn’t work. I already knew it was impossible to get a signal anywhere near that house, and that she’d never leave her girls. I listened to her pacing back and forth for a while, then she searched for them again. When she accepted that they could not be found, Cat burned the note and Rachel’s photos in the fireplace downstairs, before returning to the bedroom. I wasn’t sure if she’d do it or not, but most mothers will do anything for their daughters. I did.

I wanted Catherine to kill herself, because then I knew everyone would blame her for the murders. She had the best motive, after what those girls did to her. I hid beneath the bed and waited, with my knife in my hand just in case I might need it. I could hear everything she did – arranging the chair, removing her shoes before climbing onto it, crying – but I could not see. It took a long time for her to put the noose around her neck, but it wasn’t until afterwards I discovered she had changed the knot. Something her father taught her how to do when they went sailing, apparently.