The platform was deserted except for the young girl, huddled on a bench under the only working fluorescent light. Despite the warmth of the evening, she hunched over, hugging a small, shocking-pink backpack to herself as though it were a hot-water bottle. White wires betrayed the earphones jammed in her ears, and even as Peterson approached, he heard the shush-shush of music played too loud.

They never learn, he thought. At that age, they think themselves invincible. 'It'll never happen to me.' She hasn't seen me, she can't hear me, and she's all alone. She could probably afford a taxi, or if she couldn't her parents could. What parent would not pay for a taxi if they saw their daughter, naive and vulnerable, sat alone at a train station?

He walked on. He was almost within striking distance before she saw him. She gave a nervous start, then looked quickly away.

Wrong! You don't look away. I could be doing anything now, taking out a knife, unwinding a garrotte, and you wouldn't see it. Looking away tells a potential attacker that you're a victim. You should make eye contact, look assertive and unafraid. You should look as though you would scream and shout and kick and bite, not like you're a little mouse that would beg in a timorous voice not to be hurt.

Peterson passed her and sat on the other end of the bench.

"Good evening," he said, loudly, so she would hear over the din they call music nowadays.

She glanced at him, nodded a silent greeting then continued her study of her feet.

If I attacked you now, you would only be able to give the haziest description to the police. You should memorise my features, and let me know that you had, to discourage any ideas of an assault. But that's not the English way, not polite, and you're just a wisp of a girl with no more self-assertiveness than a mouse.

"It's dangerous," he said, in his competing-with-an-MP3 voice.

She pulled an earpiece out, sharing the upper registers of the cacophony with Peterson.

"Sorry?"

This time she did look at him. Peterson saw the judgement in her eyes. He knew what she was seeing: an old man with old values and no idea what it was to be young. He saw the dismissal of any threat in her eyes. Never mind that he was only fifty, still young enough to be 'sexually active', whatever that medical euphemism meant. Never mind that, 'old' as he was, he could still easily overpower the slightly-built girl.

"Travelling alone, at night. It's dangerous. Couldn't any of your friends have given you a lift?" Couldn't your parents? Don't they care, or don't they know you're out on your own, vulnerable to anything the night hides?

He saw the 'up yours' look on her face that said, 'it's none of your business.' "I'm okay," she said, adjusting the position of her backpack as though she were nervous of him stealing it.

Better. At least you're become aware of a potential threat. But stealing your bag is nothing. If I was to try, just give it up and run, screaming, and hope the emergency phone on the platform is manned at the other end. Anything in your bag can be replaced. Your life can't.

"Okay, but there's been some murders in the county recently. Haven't you heard? It's dangerous for anyone to be out alone at night these days."

She gave him a look of contempt, as though she despised him for trying to scare her, and screwed the earpiece back in. But she needed to be scared. Scared was the only reasonable state of mind to be in these days. Not that you should look scared, oh no. But you should be scared enough that you took sensible precautions. Be aware of your surroundings. Take note of people around you. Avoid being stuck all alone late at night on a deserted platform with a stranger.

Peterson shook his head. They said you couldn't teach an old dog new tricks, but that was easy compared to trying to teach something to kids. In their ignorance they thought they knew it all. They thought it couldn't happen to them. They thought they were invincible, invulnerable, eternal.

They were wrong.

He stretched his legs, looking around the deserted station. There was no-one on the opposite platform. Had the last train already gone in that direction? This platform was deserted too, and it was unlikely that anyone else would appear, not at this time of night. It seemed as though they were the only two people left in the world.

If she were sensible, she should move away. Move down towards the other end of the platform, away from him. Scream at him if he made a move to follow her. Hit the speed dial on her mobile phone for the police. Did she even have the police number on her speed dial?

Kids today! They were too naive for their own good.

For their own safety.

The train rumbled into the station, the warm carriage lights igniting the cold dark platform. The young girl got up and walked towards the rear of the train, entering a carriage containing half a dozen other passengers. That was better; that was sensible. She didn't know Peterson. She should avoid him. Peterson climbed into the carriage that stopped opposite the bench.

***

The girl sat on the carriage seat, hunched over, hugging the backpack to herself. One per night. That was her golden rule. Only one. She felt the reassuring bulk through the backpack, the hard rigidity when she pressed against the material. That old man was creepy, like her dad had been. She felt her skin crawl when he talked to her. She had felt sick when he had insisted on talking to her, even though she hadn't done anything to encourage him. But she had to limit herself to only one. More, and they would catch her. She noticed the spot of crimson on her wrist, and pulled down her sleeve to cover it. She could feel the edge of the blades, even through the material of the backpack and the kitchen towel that covered them.

Maybe next week, he would be there again.