I frown. ‘Why do you need to worry about me?’

‘I meant . . .’ She twists the ring on her index finger. My dad gave it to her. It’s a sapphire, and beautiful, and even though they split up years ago she never takes it off. ‘It’s just in general, you know. That’s a mother’s job.’

Why do I get the feeling there’s something she isn’t saying?

The sun bursts from behind a cloud, bright and blinding, and I have to pull the visor down. But Mum is right. I am anxious. I’m anxious about throwing up my decaf tea and half a piece of toast, about seeing the police, about Gran’s interview. About what she’ll say.

When we arrive, Gran is sitting in her usual chair in the corner of the day room. Sun streams through the glass and it feels too hot and airless in here. The French windows are firmly closed and Gran is wearing a pink jumper. She must be boiling.

She’s not doing a puzzle today. Instead she just gazes out of the doors, deep in thought, at the gardens beyond. I wonder what she’s thinking about.

‘Gosh,’ says Mum, putting a hand to her throat. ‘She looks so much smaller and thinner than when I last saw her.’ Her voice catches.

I swallow my nerves and check my watch. It’s just gone ten. The police said they’d arrive about ten thirty.

Joy, the manager of the care home, a thin, officious woman in her late fifties, strides over to where we’re hovering in the doorway.

‘Rose is having a good day,’ she says. She smiles but it doesn’t reach her eyes beyond her horn-rimmed glasses. She always has an air of harassment. ‘I’ll let you know when the police arrive. I don’t want them coming in here and distracting the other residents.’

Mum nods, thanks Joy, and we wander over to Gran. There’s a cane two-seater sofa next to her and we squash onto it together.

Gran doesn’t look up as we join her, continuing to gaze off into the middle distance. She has her false teeth in. I’m so used to seeing her without them that the effect changes her face shape, accentuating her jaw and making her look sterner, somehow.

‘Hi, Gran,’ I begin, shifting my weight towards her. I’m sitting closest to her.

Mum leans across me and reaches out her hand to take Gran’s. ‘Lovely to see you, Mum. You’re looking well.’

But Gran turns and frowns at Mum. Her face is blank. ‘Who are you?’

My heart sinks.

‘It’s me. Lorna. Your daughter.’ Mum’s voice wavers.

Panic flutters across Gran’s face. ‘I don’t have a daughter.’