I sit on my bed with my earbuds in, listening to music and flicking through the photos I took at Brandon’s tonight. Selfies of Katie, Liana and I with our faces squished together. Was being at Morrison High the main thing we had in common? Is that all it takes to end friendships, a change of habit or routine? I thought we were stronger than that.

A hot whoosh of air rises through the vents in the floor and I realise that Sam has sneakily turned the heating on even though I tell him all the time we can’t afford to turn it on every night.

When I go to the control panel in the dark hallway to turn it off, something shifts in the very corner of my vision, in the shadows.

My heart leaps for a brief moment, before I realise it’s Sam, shuffling slowly out of his bedroom. A white smudge in the dark corridor, arms dangling by his sides. His eyes are open but he doesn’t see anything.

I catch up to him in the middle of the living room, swaying uncertainly.

‘Back to bed, Sam.’ I take him by the shoulders and try to steer him gently back towards his room.

‘I saw him,’ he mumbles. ‘Hiding…’

‘You’re sleepwalking, buddy. Come on.’

I walk him back to his room and tuck his covers around him after he lies down. I switch his old nightlight on, still plugged in at the socket, and stars made of light oscillate around the room.

The sleepwalking started just over a week ago, around the time the media started calling Yin’s abductor Doctor Calm. The name has invaded Sam’s brain, we don’t know how, because we’ve made sure he doesn’t watch the news. They’ve probably been talking about it at school.

We keep finding Sam in random locations around the house, asleep and confused. He’s fine during the day, but at night he roams.

I return to my room and check the latest news reports—my sick new ritual before going to sleep each night.

After four weeks most of the information is old. The only new thing is a sketch of a house that police say could be Doctor Calm’s, made from evidence given by Karolina Bauer.

It’s disconcerting how ordinary the house looks.

The bedroom has a double bed, two bedside tables, matching lamps with yellow lampshades. Striped drapes, tan carpet. A door to an ensuite bathroom.

White and tan tiles. Shower over the bath, half-screen door. Sink and vanity, wall radiator. Small frosted window up high, too high and too small to climb through.

It could be anyone’s house.