I turn up the TV to drown out the sound of arguing and sit under the tent I’ve made from my quilt and chairs. Liz keeps dismantling it and making my bed, and I keep putting my tent right back up as soon as she’s done. She says this is my home now, but how can it be if I’m not even allowed to have my room the way I want it? Under here in the dark, reading comics by the light of my Transformers torch, is the only place in the world where I feel safe.

“Stop yelling!” I plead, rocking back and forth as Dad and Liz shout at each other in the living room. “Please, just stop!”

Angry voices follow me everywhere I go, and even the noise of my own racing thoughts isn’t loud enough to shut them up.

The smartphone Dad bought me pings from somewhere under a pile of school books, making me jump. I find it after a bit of rummaging, and I see I’ve missed a video call from Mum. I should ring her right back, but my finger hovers over the call button, and I can’t make myself press it. She’ll ask me how things are going, and even if I tell her everything’s great, she’ll just end up getting upset.

Mum always knows when I’m lying.

I scroll through the pictures she’s sent, trying to ignore the stabbing pain right through my heart at the way she’s smiling and the way Chris has his arms draped round her. I don’t want Mum to be sad. It’s been a long time since I’ve seen her looking so relaxed, and I know that’s all my fault for being so difficult.

But the funny thing is, I don’t want Mum to be happy either.

I don’t want her having the time of her life in sunny California and forgetting all about me. I don’t want Chris taking my place as the most important person in her life. I don’t want to wake up every morning in a different house half a world away and eat my breakfast with a different woman who isn’t Mum and who doesn’t know how to cut my toast the way I like it, and who doesn’t laugh when I tell her Mum’s favourite jokes.

I don’t think the universe cares very much about what I want, though.

“Jamie, turn that TV down!” Dad yells from the hall. I press the volume button quickly, hoping he’ll come in for a chat and tell me everything’s alright again, but he doesn’t. I hear the front door slamming and the sound of his car engine, and I know things are really, really bad.

He used to go for long drives on his own before he split up with Mum. I think it was his way of avoiding arguments. I wish I could drive. Maybe if I went fast enough I’d be able to zoom away before I had my meltdowns, then Mum wouldn’t have had to go all the way to America to avoid them.

It’s getting hot under my tent. I crawl out and look for something to do that’ll help me forget the game I spoiled and the shouting I caused. I flick through the TV channels, but there’s nothing on. I can’t be bothered reading, and I don’t understand my homework, and Liz has confiscated my games console cos I got too many sad faces on my behaviour chart, and…

I’m bored.

I wish Dad would let me take medicine for my ADHD. It would be nice to have an ordinary brain that wasn’t always fluttering off when I needed to use it. Maybe when I grow up and I’m a mad scientist I’ll be able to make my own cure for ADHD.

Hey! That’s a great idea.

I grab my chemistry set and get to work, mixing up a whole load of chemicals in test tubes and trying to make something that won’t taste like decomposing skunk. I figure if my brain is fizzing like cola and mints then I need something that’s going to neutralise it. I know all about acids and alkalis, and last year I worked my way through a big book full of experiments to test how different chemicals react with each other.

I know how to fill a balloon full of carbon dioxide by mixing lemon juice and baking soda in a bottle.

I know how to make water glow in the dark by soaking a highlighter pen in it and shining an ultraviolet lamp through it.

I know how to make a lava lamp with vegetable oil and water and fizzy aspirin tables that make the oil bob up and down.

The only thing I don’t know is what’ll happen when I drink the strange brown liquid I’m measuring out into a beaker.

A few seconds later I find out, and it takes nearly a whole roll of toilet paper to clean the sick off my best trainers.

OK, no more experiments till my stomach stops bubbling like a witch’s cauldron.

I leave my science kit spread out all over my table and go and sit on my bed, flicking through the TV channels again and feeling like a failure. I wish I could do something right, something good for once. I wish I could prove I’m not always a selfish monster who makes everyone upset. I’ve already wrapped up my Transformers torch to give to Elin for her birthday, but I don’t think that’s going to be enough to stop her hating me.

Then I have a genius idea.

I know exactly how to make someone else happy for once! I can’t make Elin happy cos all her riding-lesson money’s been blown on my stuff, and Mum’s far off in California, and I’ve no idea how to fix Dad or Liz and make them stop yelling at each other. But there’s someone else who deserves to have something nice happen to them.

I tiptoe into the kitchen like I’m James Bond on a mission. I find what I’m looking for inside the stationery drawer, and carry one of the precious cards back to my room.

It takes me ages to fill it out, and I get some chemical stains on the envelope, but I’ve used my best handwriting so most of the words are on the line and they aren’t all running into each other for once.

I grin as I slide the card into the damp envelope and put it in my schoolbag for tomorrow.

Elin’s having the best birthday party in the world on Saturday, and I’m going to make sure the nicest person in the world will be there.