When I come round, I’m not even sure that I have come round. My head is hurting really badly, especially at the back, like I’ve fallen backwards and banged it. My eyes are stinging and I daren’t try to open them, and there’s something cold on my cheek, which I take to be the floor. There’s also something around my neck, tight.

Yet – so far so good – is the first thing I think. Then: I’m going to open my eyes soon, and I’ll be back in my room shortly before this whole thing started.

I open my eyes dead slowly. Am I in my room? The cord of Alan Shearer’s box has twisted round my throat, but I can loosen it, and Alan Shearer’s unharmed, which I’m relieved about. But still …

I am in my room. I know I am because I am staring upwards out of the window and I recognise the tree in next door’s garden and the line of the roofs opposite. This is the room I left, with Mum pounding on the door, and Grandpa Byron’s face in the window as I disappeared. I sit up and rub my eyes and do that thing when you ask yourself if you’re in a dream just to make sure you’re not in a dream.

I am not in a dream. Also, this is not my room after all. The door’s in the same place, the view out of the window is the same, but the bed is along the other wall, there’s a different duvet cover on it, the rug is different, there’s a poster for a band I’ve never heard of on the wall …

So whose room is this?

From downstairs comes the sound of a television, and from the next room the sound of a shower. Removing my feet from the zinc buckets and standing up, I go to the window.

“Oh my God,” I mumble to myself. “This is my room.” Outside is the little back garden I look at every morning, the house next door, everything is as I had looked at it last from this position.

I look around the room again, just to check, and at first I think Carly must have moved into my room while I was away in 1984.

But I set the return time to exactly when I left. By rights, Mum should be thumping on the bedroom door, Steve shouting at me, Grandpa Byron’s mouth forming an astonished ‘O’.

Then the bedroom door opens, and in walks Carly in a dressing gown, towelling her hair dry and she doesn’t see me at first.

“Hi, Carly!” I say. That’s when she does see me. Her eyes widen and she emits a shriek; a long scream of absolute terror.

“Hey, it’s OK, Carly, what’s up with you?” I ask.

“Who … who are you? Get out! Get out! Take what you want. Take it, just don’t … just go.” She’s trembling and her voice is shaking. I stay by the window.

“Where’s Steve? Where’s Mum?”

“My boyfriend’s downstairs and my dad’ll be back any minute, really he’s just gone to the corner shop. He’ll kill you. Jol! Jolyon!” She’s shouting really manically.

“Carly! Stop it, why are you being …”

At that moment, things get really hairy because I hear pounding footsteps on the stairs and into the room bursts Jolyon Dancey who looks at me in puzzled anger. “Who are you?” he snarls. “What are you doing in Carly’s room?”

“It’s me – Al,” I say. “You know – Carly’s stepbrother?” Then – desperately – “The hamster fancier?” His face screws up in utter incomprehension, and a kind of wariness.

“Get him, Jol – do your karate on him!” Jolyon immediately adopts a weird martial-arts stance, feet apart, legs bent, hands aloft. It’s almost comical and I expect him to go, “Hi-yaaa!” but he doesn’t. He just stands there with a tough expression on his face, and that’s how we stay for the next few seconds until Carly says, “Well go on then, Jol – get him!”

“Shut up, Carly!” I yell at her, and it seems to do the trick. She stops, and just stands there, her bottom lip wobbling, and tears welling in her eyes. “What have you done to my room?” I ask her.

There’s a pause while Carly looks at me, pleadingly. “Just go, please!”

The fear in her voice is genuine, and I’m scared that Carly has gone a bit off her rocker, and when people go a bit crazy there’s no knowing what they might do – they’re unpredictable. She was always heading that way, I suppose: teenage angst and all that. I try to slip past her and get to the door, but Jolyon blocks my way, still waving his hands around, trying to look menacing. “I’m a green belt. You don’t want to tangle wi’ me.”

He is right, I don’t, but the way he’s standing, with his legs wide apart gives me a chance. I turn my head to look out the window, then I point and say, “Oh my God!”

It works. They both turn to look and in that instance I draw back my foot and deliver a swift, hard kick right between Jolyon’s legs. The sound he makes is horrible: a high-pitched squeak and a breathy gasp at once. I feel sorry for him as he keels over sideways, clutching his groin and retching. I have plenty of time to pick up Alan Shearer’s box, take the black box from the bucket and put them both in my backpack and leave through the bedroom door. Carly looks utterly terrified and I feel bad for that.

The stair carpet is different. It’s the same one as when me and Mum moved in, then it got changed. I crane my head to see if Mum’s watching telly, but she isn’t and I guess she’d have heard the commotion.

It’s the same house, all right. But so many things are slightly different, not just the stair carpet. Things are arranged differently. The picture of Mum in a frame on the hall table isn’t there, the coats on the rack are different.

Halfway down the street I see Steve coming towards me, carrying a bag of groceries. He’s grown a goatee beard in, like, a day, which doesn’t suit him.

“Steve! Steve!”

Steve stops. He looks at me with a half-smile. “Hello.”

I stand in front of him, and take on the same half-smile, and say, sort of conspiratorially, “Um, Steve, I think Carly’s going a bit y’know … I dunno … cuckoo?”

Steve squints at me quizzically. “What?”

“Carly. She’s just screamed at me to get out of the house.”

Steve shakes his head. “Sorry, son, but, erm … who are you?”

I give a little sigh.

“Steve, man – c’mon. I’m really … I’ve had a mad time lately, and I don’t want to do this.” Steve has started to walk on now, and I keep up with him. “It’s just Carly was being all weird with me, and well … I just …”

“Are you a friend of Carly’s? Have you been round our house before?”

“Ste-eve!” I’m getting bored with this now.

“Look, I’m sorry, son, I don’t have a good memory for Carly’s friends. What’s your name again?”

“Stop it!” I’m truly impatient now, and I snap the words out.

“Hey – watch your step, son.” We’re outside our house now, and walking up the front path. “You wait, and I’ll tell Carly you’re here.”

“Steve! Stop it!” I’m shouting now, and really upset. “Where’s Mum?”

Steve turns to face me now, with his back to the front door.

“I think, son, you need to go home.”

“What do you mean? This is my home!”

Steve stares at me for a moment.

“Go on, son. Off you go. You’ve had your fun. Go now.”

“What? No! Where’s mum? Is she working late? Is she out with Annika?”

“This is your last warning. Now. Piss. Off.” He’s not shouting, but his voice is menacing and when he turns to let himself in the door, I’m left standing in the middle of the path, blinking hard and gulping and holding a box with a hamster in it.