Ellie relived the moment — her break from the pack, her shot on goal, the shocked look of the goalie as the ball soared past him, just out of reach, and the deafening roar of the crowd, so powerful that she could feel it like waves drumming on her body — and shook her head. This was a boy's memory. The other players were all male and the leg that had kicked the winning goal was hairy. Yuck.

Something cold was creeping into her stomach. A thing like this could only have come from Jamie. Jamie was probably the most irritating younger brother in the world but he was still her brother.

Credit: JACEY

She knocked on the door of his room and then stepped well back. You never knew what might be on the other side.

Jamie's room was even weirder than when Ellie had visited last. There were more computers, many of them torn open, and other machines she could not identify. Jamie was working on one that looked different. It was scuffed white instead of matt black or grey and its open top and missing side revealed rows of tiny cylinders interconnected with coils of thin tubing.

There was something that looked like a big mechanical dog wedged between two boxes of parts on the floor. She placed her feet carefully, partly out of general caution, partly because she had just treated herself to a new pair of shoes.

She gave him her best no-nonsense stare, modelled on the one Mum used on them. He flinched.

“I remember kicking the winning goal in a big football game.”

“Oops. It must have leaked out. I'll put a towel under the door next time.”

The olfactory nerve is a direct extension of the brain so memories were administered in nasal sprays. The thought of Jamie's bootleg memories wafting down the hall frightened her.

“Jamie!”

The dog had come to life. She pointed at it. Its head turned, tracking the movement of her hand. It had fangs.

“Don't move. It can only see things that move quickly.”

Jamie reached out slowly and smoothly and hit a key on his computer. The dog collapsed, inert.

“Where did you get that memory?”

“Made it.”

Her stomach lurched. Only doctors and the police were allowed to manufacture memories. Even teachers had to have forms signed and countersigned before they could so much as administer a memory. This was serious stuff, worse than drugs. The police could arrest Jamie for this, would arrest him if they found out. Jamie would go to jail if they caught him.

Implanted memories made society work. Someone who was aggressive was given memories of peaceful acts, a cheat was given memories of honesty. Sometimes it had to be done many times before the person's behaviour changed to match what they remembered. But society had to control what was implanted, not individuals. She had learnt that at school.

“We need to talk.”

“Can't talk now. Big fight comin' up.” He was loading two ugly bricks of scarred metal and plastic into a bag. They had armoured wheels and sharp things that slid out of their interiors. Every week he went off to fight these things against ones made by other boys almost as weird as him.

“You need to tell me now.”

He kept on loading the bag with batteries, tools and spare parts as he talked. The story came out in bits and pieces. He had found the machine while scavenging at the local tip. It was broken and obsolescent, discarded by a research lab. The tip attendant had no idea of what it was and accepted £5 for it as scrap.

“It wasn't hard to fix. Just a blown motor-driver chip and a pump that seized when its motor stopped working.”

“It's got to go.”

“No way. This is a once-in-a-lifetime thing. I'll be careful. Besides ...” He pointed at the banks of tiny cylinders in his prize, each with its own bar code. “When the reagents run out, that's it. These chemicals aren't something you can order without attracting attention.” He shouldered the bag; they went out into the hall and then he turned. “Do you want to come and watch me fight?”

After he was gone she went back to her room and had a long hard think about what to do.

Ellie woke the next morning feeling pleased with herself. She hadn't liked the idea of sneaking into Jamie's room but some things just had to be done. She relived the memory — she had crept into the room, moving slowly, careful to disturb nothing, and had triple-wrapped the machine in black plastic garbage bags. It had made a series of crashes, each fainter than the last, as it tumbled down the garbage chute. She would have to face Jamie at breakfast but at least he hadn't been pounding on her door or phoning her.

She brushed her hair and put on her best dressing gown. Ellie knew she had done the right thing and had saved Jamie from the consequences of his very silly actions. But he would be disappointed and angry, and was probably sulking. Still, he deserved an explanation and she wanted to get it over with. She knocked on his door.

“Go away Ellie. I'm busy.”

She glanced down. There was a towel stuffed under the door.