When Mary comes outside she’s got shoes on, a jacket and a khaki hold-all. ‘Mobile number’s on the kitchen table, with the phone. Here are the keys.’ She puts them in my hand. ‘Ring me.’ She’s fumbling in her bag, moving too slowly. I want to scream at her to hurry. ‘Why don’t you come with me?’ she says. We could both—’

‘I can’t. Go to your parents’ house and—’

‘My parents?’ She blinks at me in the darkness.

‘Go to my house.’ I pull my keys out of my bag and throw them at her. ‘Ring the police, ask them to wait with you.’

At last she gets into the taxi. ‘Ring me,’ she says before closing the door. ‘Take care of yourself.’

I watch as the cab turns and drives down the long path, over the discreet speed bumps that look like small hillocks in the concrete, and out through the school gates. Once it’s gone, I run back to the cottage. Mary left the door open. The music’s still playing. I run to the dining room and turn the door handle, but nothing happens. I turn it the other way. Nothing. Locked. I reach above the door frame for the key, but there’s nothing there. Frantically, I sweep my fingers all the way along the tiny ledge. The key’s gone.

I run back to the kitchen, where I’ve seen other keys hanging from small hooks on the underside of a wooden cabinet. Yes—five metal hooks, screwed into the wood. More than five keys. I try them one by one, sprinting between the two rooms, but none of them’s the right one. I’m going to have to smash the window.

I run past the kitchen table, where Mary has painted her mobile number in blue on the wood; there’s a thin blue-tipped brush next to the cordless phone. Outside, there’s no one around. I can see lights in some of the windows of the main school building in the distance, the one with the square tower, but they seem a million miles away.

At the back of Garstead Cottage it’s darker than at the front, without the lights on either side of the path. There’s a window that must belong to the dining room—it’s the only one that’s the right size. I bend to pick up a large stone from the ground and find myself rearing back. I can’t pick up a stone and throw it. I can’t. What else can I use? My shoes aren’t heavy enough, nor is anything in my bag.

The bikes at the front. I sprint round the side of the house and find, near the bikes, something even better: a metal tyre pump. I grab it and run back to the dining room window.