‘Oh, I can see now,’ she says, her voice muffled as she grabs whatever it is from the other side of the door. ‘You must have dropped it on your way out.’

She opens the door fully and as I step towards her my knees buckle. She is holding a tiny purple cardigan. Elspeth’s school cardigan.

‘It was just this blocking the door,’ says Sonia breezily. ‘As I said, you must have –’

‘Give it to me,’ I say, yanking it from her hands.

I press the cardigan to my face but there is no trace of Elspeth. The cardigan smells of an unfamiliar fabric softener, one I don’t use. Someone has washed it. Some stranger.

‘Maggie, what’s the matter?’ asks Sonia, closing the door behind us as I walk into the living room.

I sit down on the sofa and spread the cardigan out on my knee. I look at the label: Marks & Spencer. Age 8–9. Elspeth always wore the next size down. She was small for her age. I pull the label up and look on the other side. Her name will be here. I remember writing it in black pen on the first day of term: Elspeth Allan. Year 5. But her name is not there. It has been washed away.

‘Maggie?’

Sonia sits down next to me and places her hand on my arm.

‘It’s Elspeth’s,’ I say, turning to her. ‘Her school cardigan. Someone’s posted it through the letter box.’

Sonia looks at me then at the cardigan.

‘Why would they do that?’ she says.

‘Because they’re holding her hostage,’ I reply, pressing the cardigan to my chest. ‘She said so in her letter.’

‘What letter?’ says Sonia.

I put my hand in my pocket and give her the letter. She opens it up and starts to read.

‘How did you get this?’ she says, handing it back to me.

‘It was posted through the door last night,’ I tell her. ‘I went to the police this morning and they seem to think it’s some sick practical joke. Elspeth is officially dead, they tell me. Sean identified her so it’s obviously true.’

‘Maggie, they’re right,’ says Sonia gently. ‘Elspeth is … she’s gone. And as for this, well, if it’s someone playing a joke then they need serious help. I mean, what kind of scumbag …’

‘She needs me,’ I say, cradling the cardigan in my arms. ‘This just confirms it.’

‘Maggie,’ says Sonia tentatively. ‘You’ve been so tired today. Maybe you took it out of one of Elspeth’s boxes.’

‘Then why would it be on the doormat?’ I snap.

‘Maybe you were holding it when we were heading out,’ says Sonia. ‘We were in a bit of a rush. You could have dropped it …’