Stranger danger.

The young blonde girl pulled on one of her plaits and stared out of the window at the climbing frame in the dirty school yard.

Just half an hour ago she'd been handing upside down from one of those monkey bars, her hair hanging down about her ears whilst she swung freely, ignoring the drop and trailing her fingers down to dangle in mid-air.

Of course, that fat Trisha Delaney had told Ms Casey that Rose was going to fall and she'd been told to stop acting like an over-grown ape and get down.

She'd got Trisha back though by pushing her into the mud and made her cry.

Rose had felt bad about that.

But when she was upside down the whole world looked really different, all exciting and strange. The sky was the floor and it looked like the light blue carpet that Mr. Drumknot had in his front room and wouldn't let them take drinks into. The grass was sort of mud brown and made a very muddy sky, like just before it rains. And everyone looked like aliens walking upside down with their feet on the sky. People's chins became their nose and their mouths didn't make the words properly.

It was funny and Rose wondered if—

"Rose Tyler, are you paying attention?"

She snapped back to the real world to see Ms Casey glaring at her

"Yes, Miss."

"Then what did I just say?"

"You said as if I was paying attention."

There was a titter of laughter and Rose found herself cringing as Ms Casey's face got red.

"I was saying, Rose, if you were listening, that we have a special treat today. Detective Inspector Carlisle has come to see us specially to talk to us about a very important subject. Very important, Rose, so you need to pay attention."

"Yes, Miss," Rose smiled and turned to the front.

Ms Casey looked suspicious at her sudden acquiescence but shook her head.

Trisha Delaney turned around and stuck her tongue out at Rose.

"You got mud on your nose!" Rose whispered fiercely and Trisha's eyes welled up.

"You're gonna get into trouble!" Max Foster nudged Rose. "Trisha's stupid anyway."

Rose smiled a little at Max, he was nice.

The door to the classroom opened and a tall thin man dressed in a dark suit strode in. His hair was the colour of the mud outside and he had smiling eyes.

Rose decided that she liked him, even if he didn't look like a policeman.

"Good morning!" he said with a grin.

"Good morning," the children chorused.

"My name's Detective Inspector Carlisle and I am a special policeman."

"You talk funny," Rose said and he looked at her with his happy eyes.

"I do, don't I?"

"And you're not wearing policeman clothes," she added, her nose wrinkling. "We 'ad a policeman stay and he had a trunch-stick and a blue uniform and a car wiv a light on. And he 'ad a badge saying he was a policeman. He looked smarter than you."

"Rose!" Ms Casey's voice was hard and Rose shut up quickly.

"It's all right," he said in his lilting voice. "Got a clever one there. Rose, is it? Well, Rose, I used to live in Scotland, so my voice is funny to you. Your voice is funny to me too. And I'm a special policeman so I don't have to wear the blue uniform, I still have a badge though and a car with a light on."

"Can I see?" Max called.

"Me too!" yelled Emma and half a dozen others.

"Quiet!" Ms Casey's voice whipped out and order was restored.

"The reason I'm here today is to tell you all about something very important. Now who can tell me what a 'stranger' is?"

Trisha's hand flew into the air.

"Yes?"

"A stranger is scary and mean and hurts you."

He winced. "Not really. Some strangers can be like that. Anyone else?"

Rose put her hand up. "My mum said a stranger is anyone we don't know. Everyone is a stranger unless she says. She said that Ms Casey was a stranger too but its okay cuz I know her now."

He hid a smile behind his hand. "Clever girl, that's right, a stranger is anyone that we don't know."

Rose eyed him. "Like you."

He looked taken aback and agreed without thinking about it. "Like me. I'm a stranger."

There was a little gasp from the children and Trisha burst into tears.

"But Ms Casey isn't a stranger and she's watching me very carefully," he added quickly. "So who is a stranger?"

"A stranger is someone we don't know."

"That's right," he smiled again. "A stranger is anyone that you don't know. It could be a man, a woman, or another child. If you don't know them that makes them a stranger. And although some strangers can be nice; a nice old lady or nice play friend, some strangers can be nasty and mean and we need to be careful.

But the trouble is, how can we tell who is nice and who is nasty?"

Trisha stuck her hand up again and Rose rolled her eyes at the irritating teachers pet.

"Nice people smile."

"They do, but nasty people can smile too. Just because someone smiles at you doesn't mean that they are nice. Bad people can look like good people so we need to understand something called "Stranger Danger."'

He sat on the edge of the table and looked down at them seriously. "Stranger Danger is very very important and there are rules. Rule number one is never, never, ever go off with a stranger. What is rule number one?"

"Never ever go off with a stranger," they echoed.

"So if you meet a man in the playground and he tells you to go with him remember never, ever go off with a stranger. Rule two; never, ever take sweets from a stranger. What's rule two?"

"Never, ever take sweets from a stranger."

Trisha pouted. "Why?"

"Because they could take you away from your mum and dad' and take you far away and hurt you. These rules are important. Rule one is never, ever go off with a stranger and rule two is never, ever take sweets from a stranger."

"Rule three is never get into a car with a stranger and rule four is never go play alone, always have someone with you."

The children repeated the rules until he was sure that they knew them.

"Now if a stranger ever comes up to you and asks you to go with him you say no. Say it loud, shout it if you have to. Say; No, I won't go!"

"No, I won't go!"

He winced at the decibels of their voice. "Well done. Loud, but well done. If someone tries to touch you who isn't a Doctor or your parents you should say no. Now if a stranger comes to you to try to get you to go with them, or asks you to help them find a pet, or tried to get you alone you should scream and shout as loud as you can. Scream and stamp your feet. You'll enjoy that!"

He gave a brave smile.

"You should run to your parents to tell them as fast as you can. If you aren't with your parents, or you are lost you need to tell someone you can trust. You can trust your teacher, or a teacher that you know. You can trust policemen or policewomen, Doctors and nurses and traffic wardens and you can trust adults that you know. Remember if someone comes to you that you don't know, tell a grown up. Never ever go with a stranger. Strangers are dangerous."

Rose put her hand up and he smiled deeply at her, his eyes twinkling.

"Yes, Rose?"

"You said tell a policeman."

"Yes, Rose."

"You're a policeman."

"I am."

"But you don't wear police clothes. You look like a stranger."

He blinked at her. "Yes, well, right. Well done. I do. But if I was a at football match I'd be wearing a yellow vest, or if you were at the zoo I'd be wearing a uniform. If you are in a place like that you can tell a guard or a security person or someone in charge. Even if they offer you nice things remember never, ever go off with a stranger."

He started to divide them into little groups and take turns in pretending to be strangers.

Rose watched him carefully for a few minutes and then let her attention turn back to the window where the climbing frame beckoned.

Never go off with a stranger.

Like she'd ever be stupid enough to go away with people she didn't know. Rose was clever; she knew that there were bad people. Like the man who'd hit her mum.

Never let anyone except a Doctor or your parents touch you.

Rob had liked to pinch her but when she'd told her mum she'd thrown him out.

Only go with people you trust. Never go off with a stranger.

Strangers are dangerous.

She leaned against the window and stared out, her mind turning over. Always say no, don't go.

"Rose?" the policeman was watching her. "It's your turn. Come here."

"No."

He laughed. "We're doing the demonstration over here."

Ms Casey rolled her eyes as Rose still refused to move. "Rose Tyler, I swear you are going to be trouble when you grow up. If you don't learn this then some dangerous man could come along and take you far away."

She was right on both counts.

It hadn't occurred to her until she'd stood on a space station five billion years in the future that she had been a bit of an idiot.

Raffalo stared at her uneasily.

"If you don't mind me asking?"

"No! Not at all. Erm... I dunno, a long way away... I just sort of, hitched a lift with this man."

There was something knocking about in her brain. Some kind of inbuilt defence that she had squashed when he'd stood there in front of his blue box. Some long forgotten conversation.

Suddenly the voice of Detective Inspector Carlisle filtered into her head, a forgotten voice from her childhood.

Rule one is never, ever go off with a stranger.

Rose froze, her head suddenly swimming with doubt.

"I didn't even think about it."

"He's not invited. What do you think? You could stay here and fill your life with work and food and sleep, or you could go, uh... anywhere."

Now if a stranger comes to you to try to get you alone you should scream and shout as loud as you can. Strangers are dangerous!

"I don't even know who he is."

A stranger is anyone you don't know.

"He's a complete stranger."

"This box isn't just a London hopper, you know, it goes anywhere in the universe free of charge."

Even if they offer you nice things remember never, ever go off with a stranger.

Her stomach was suddenly twisted up in knots and she felt like an idiot. After all her bravado she'd done exactly what she'd said she'd never do. She'd gotten into a strangers car/ TARDIS and gone off with him.

She'd even asked him if his life was dangerous and he'd said yes. Yes!

Raffalo looked worried and Rose jolted. "Anyway don't let me keep you."

Raffalo said something but Rose was far too preoccupied to answer.

She left quickly and found a quiet place, watching the Earth as it heated up.

Well it wasn't like she could run back and tell a grown up as she didn't actually know any here. They weren't exactly people after all. They were alien.

Detective Inspector Carlisle never brought up this scenario!

A scared giggle bubbled from her mouth.

Oh god, she was an idiot.

She didn't know him he could have been anyone. She'd worked herself up into such a state that by the time the Doctor found her she was almost hysterical.

"Who are you?" she demanded, "Tell me who you are."

But he hadn't. He'd shown her.

He'd saved her life and the life of those on the space station.

He'd let her talk to her mum and he'd taken her home. Standing on the streets of London watching people go by he'd asked her if she wanted to stay.

Always say no, don't go.

But was that what she wanted? Life with a dangerous stranger. A stranger who'd saved her life and took her to wonderful places and he hadn't hurt her. Even the policeman said that some strangers were nice.

"I don't know. I want..."

I want things to be simple. I want good men to wear white and bad men to wear black. I want things to be easy and clear.

He looked so alone, so frightened that she'd say no.

Rose Tyler, one day a man will take you far away!

Who was she to argue with Ms Casey?

"Oh! Can you smell chips?

"Yeah. Yeah!"

"I want chips," Rose decided.

Things were that simple.

Besides even Detective Inspector Carlisle said you could trust a Doctor.