‘I sprained my ankle yesterday,’ I say, feeling a flush spread across my face.

‘Did you?’ She turns and stands in front of me, forcing me to stop. ‘Sprained ankles generally swell to twice their size. Yours doesn’t look swollen. It looks to me as if it’s your foot that’s sore. Has someone hurt you, Ruth? You seem very far from all right to me. Has your boyfriend hurt you, maybe?’

‘Aidan?’ I think about the way he kisses the straight line of pink scar tissue that starts below my ribcage and runs down over my stomach. He’s never asked what caused it, neither on that first night in London nor since.

He is incapable of harming anybody. I know he is.

‘Aidan?’ Charlie Zailer repeats. ‘Is that your boyfriend’s name?’

I nod.

‘Has Aidan hurt you?’ She folds her arms, blocking the corridor so that I can’t pass her. I don’t know where we’re going anyway; I have no choice but to wait.

‘No. I’ve got a . . . a bad blister on my foot, that’s all. It hurts when my shoe rubs against it.’

‘Why not say so, then? Why pretend a blister’s a sprained ankle?’

I can’t understand why I’m out of breath. I clench my teeth, against the pain in my foot and against her attitude. Knowing what she’s been through, I expected her to be kind. Understanding.

‘Here’s what we’re going to do,’ she says in a loud, clear voice, as if she’s talking to a small child. ‘I’ll settle you in one of our reception rooms, sort us out with some tea, see if I can find a plaster for your foot . . .’

‘I don’t need a plaster,’ I say. New beads of sweat prickle my upper lip. ‘It’s fine, honestly. You don’t need to—’

‘. . . And then we’ll talk about your boyfriend. Aidan.’ She starts to walk again. I have to half run to keep up with her. Is it a test? The pain is constant now; I picture a wide, weeping gash beneath my toes, with whatever caused it embedded in the wound, pushing its way deeper in with every step. The effort I’m making not to think about it is like a tight thread in my mind, winding tighter and tighter. My eyes ache to close. I’m aware of the sound of my breathing, of the air rushing out of my lungs and having to be dragged back in.

I follow Charlie Zailer round a corner and we are in another corridor, colder than the last, with windows all along one side. No pictures here, only a row of framed certificates, all with some sort of official-looking stamp on them, but they’re high up on the wall and we’re going too fast for me to read the writing.

I stop when I see a pale green door ahead. I’ve done this before: walked down a long passageway towards a closed door. Green. Dark green.

‘Ruth?’ Sergeant Zailer is calling me, snapping her fingers in the air. ‘You look as if you’re in shock. What’s wrong? Is it your foot?’