Disclaimer: Yes, I own ... this ... and, um, well, the plot, is really about all I own ... Belle and I own the whipped cream, if that counts? No? Ah well. All hail JKR.

A/N: Nymphus!! My first ever Nymphus fic, so be kind to me? Please:) But seriously, this is another of those random thoughts that just sort of come to me and I have to write the fic or it drives me insane - I've had this in my head for a week. And now I'm talking about owning whipped cream. I believe my point has been proven.

Reviews: If you feel so inclined, then I accept constructive criticism - I can even handle flames!

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"And Dumbledore's agreed to this?"

"Only he and McGonnagall know who you really are – everyone else will treat you like a regular student. Which means no showing off your magical skills!"

"Not even a little bit?"

"Tonks …!"

"All right, all right! I'd better go get ready, then – I'll need to shrink all my clothes and dig out my old robes, I guess. And come up with a disguise!"

"You'll be fine. Dawlish and I'll meet you at King's Cross tomorrow morning – be there are ten-thirty sharp. We want to go over a few things before you leave."

"Got it. See you tomorrow, Kingsley."

Nymphadora Tonks – known by her surname to all those who enjoyed the privilege of breathing – hung up her phone looking irritated. Last-minute missions were to be expected in her line of work – she didn't sign up to be an Auror for the paperwork and small cubicle that apparently constituted an office – but this was ridiculous. A last-minute mission that would last her an indefinite period of time – a live-in position, nonetheless! She grumbled to herself as she raided her wardrobe, shrinking all her clothes to roughly the size a thirteen-year-old girl might wear, and digging out the Hogwarts' school robes she hadn't worn in nine years. She transfigured her old yellow-with-black-stripes Hufflepuff tie into a red-with-gold-stripes Gryffindor one. She felt like such a house-whore. But, it was all for a good cause … Well, as good a cause as any, at least.

She was to go undercover as a student at Hogwarts' School Of Witchcraft And Wizardry – a Gryffindor student, nine years after she had already graduated as a Hufflepuff. And since then she had become a trained Auror for the Ministry of Magic – fair enough, it had taken her longer than most to qualify, after taking a few years out to travel, and then almost failing her Stealth and Tracking exams. But she had done it all the same.

And why was she being sent undercover? Well, to keep The Boy Who Lived, just that – alive. Notorious mass-murderer, Sirius Black, had escaped from Azkaban prison, and word inside the Ministry was that he did so for the purposes of killing Harry Potter. His own godson, whose parents he had supposedly betrayed to You-Know-Who. There was one tiny problem with Tonks' new assignment, of protecting Potter and catching Black. Deep down, she didn't really believe Sirius had done anything wrong. She still believed him to be innocent – he was, after all, her mother's cousin.

Her favourite cousin, and Tonks' favourite babysitter as a child. He was always so much fun, and he came bearing not only chocolate – although that in itself was reason to worship him – but tales of his many, many wrongdoings at Hogwarts. But they were always harmless pranks, and usually hilarious. Never anything involving the Dark Arts – and certainly nothing to suggest he would ever betray his best friends. Then again, the whole Black family had been Slytherins up until Sirius – and his younger brother had been a Death Eater, supporting the Dark Lord. It wasn't THAT much of a stretch to imagine he had gone bad too … it just hurt.

Shaking those thoughts from her brain, Tonks waved her wand in a sweeping motion around the room, and clothes from all around her flew into the open trunk at her feet. She opened the parcel Kingsley Shacklebolt had sent her via owl earlier that evening, right before contacting her via Muggle telephone. Inside were all the books she would need for the next academic year at Hogwarts – joy. She shoved them into her trunk along with her cauldron and a few quills, bits of parchment – the usual rubbish. She then slammed it shut and decided it was time for bed – and a moment later, managed to trip over the trunk, stubbing her toe AND falling flat on her face. Thank Merlin she lived alone, she thought grimly, clambering into bed with all her clothes on.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

"Now, you're sure you know what you have to do?" Kingsley asked for the fourth time.

"Yes!" Tonks straightened her school skirt uncomfortably, tugging her cloak tighter around her. "Owl you once a week and keep an eye on the Prophet for news. It's not hard."

"Just make sure you stick to the Potter kid like glue," Kingsley said quietly. "If Black really is after him, he's more likely to do it in school than around a bunch of Muggles."

"I still don't think he'd be stupid enough to attack Harry right under Dumbledore's nose!"

"We don't know what he'd do – he's a madman," Dawlish said in his slow drawl.

"You just take care of yourself, Nymph –- Tonks," Kingsley amended quickly. "And have a good term!" he added more loudly, as a crowd of parents passed. Tonks rolled her eyes.

"Shut up, Shacklebolt," she said warningly, as he sniggered at the sight of two identical redheaded boys walking past and giving disguised-Tonks the eye. "Just, shut up, or I'll hex you into next week, and tell my classmates my Uncle Dawlish taught me how!"

"You'll do nothing of the sort, Tonks," Dawlish said monotonously. "You're an underage witch now, remember? No magic until you're safely inside Hogwarts grounds."

Tonks shot her colleague a scowl as she tucked her wand inside her robes for safekeeping.

"It was a joke, Dawlish," she said witheringly. "Sort of," she added in a whisper to Kingsley as she pushed past Dawlish to make her way onto the train. Shacklebolt grinned.

"Hogwarts must have seen enough of you already, Tonks. Don't ask me why they agreed to take on more! But seeing as they did … good luck. And watch out for Black. I know you've been well trained, and I know he's after Potter … but like Dawlish said, we don't know what he's capable of doing, even to an innocent child. Just be on your guard."

"Always!" She gave Kingsley a wink, threw another glower in Dawlish's direction, and turned and boarded the familiar red steam train.

It didn't take her long to find her target – he and another boy, with flaming red hair, and a girl with bushy brown hair, were trailing up the train just ahead of her, looking for seats. She hung back for a few moments, and then followed them, right up to the last carriage, where they finally entered. Tonks counted to ten in her head, before double checking her disguise in the train window, and sliding open the carriage door. All three teens looked up.

"Hi," she said nervously. "D'you mind if I have a seat? Everywhere's kind of … full."

"No, sure, sit down!" said the redheaded boy, perhaps a little too eagerly, as the girl glared at him pointedly. "We've got plenty of room – haven't we, Harry?!"

"Uh, sure," Harry Potter said, smiling at her. "Come on in, have a seat. I'm Harry."

"I noticed!" Tonks said, sitting down right across from him. "You're Harry Potter!"

"Yeah," he said, looking around slightly uncomfortably. Damn! Idiot Tonks, she thought.

"Wow," she said, feigning thoughtfulness. "I always thought meeting a celebrity would make me all tongue-tied and stuff. But it's funny – you don't seem all that special to me."

The redheaded boy snorted with laughter, and to her great relief, Harry grinned.

"This is Ron Weasley," he said, indicating his friend, "and Hermione Granger."

"I'm Tonks," she said chirpily, and all three stared at her sceptically.

"Tonks?" the girl named Hermione repeated. "That doesn't sound much like a name."

"It's my last name," she admitted. "My mother had a twisted sense of humour, and I hate my first name. I've gone by my surname since I was at Hog – uh, since I was six."

Moron! She cursed herself. She had almost blown her cover already.

"So what is your first name?" Harry asked curiously, a grin still firmly fixed on his face.

"Not telling," she laughed, sticking out her tongue. She glanced to the only other occupant of the carriage – an older man, sleeping quite soundly in the corner. She jerked her head.

"Who's he?" she asked, undoing the top fastenings of her cloak – she'd forgotten it itched.

"Professor R. J. Lupin," Hermione replied instantly. Tonks felt her throat close up.

"Lupin?" she repeated, suddenly wanting to get the cloak unfastened quicker. She was extremely warm, now she thought about it.

"That's what it says on his case." Ron pointed to the battered suitcase in the overhead compartment. Tonks muttered a whole string of curse words, several of which were apparently new to the three teens, as they stared at her with mingled expressions of shock and bewilderment. Of all the people in the world to be on the train!

Remus John Lupin – it was him all right. She recognised him now: older, greyer, and far more lined than the last time she had seen him, about twelve years ago, but still with the same strong jaw; the same laughter lines around his mouth; and the same brownish hair flopping over his eyes. Not only had he been Sirius' best friend – a problem in and of itself, now that Sirius had escaped from Azkaban: Remus would be a suspected accomplice if he placed himself at the school – he had also been her first crush. Fair enough, he was eight years her senior, but that was nothing, not in the grand scheme of things.

But – she thought with a sickening jolt – if he remembered her too, he would know this was just a disguise. He would recognise her name – curse her mother! What kind of a name was 'Nymphadora,' really, anyway? – and he would most certainly know she was no longer thirteen years old. She had been older than that the last time she had seen him, for Merlin's sake! This was the kind of problem she did not need one day in.

"What's going on?" Ron hissed suddenly, and Tonks was jolted back to reality. The train had stopped, and outside, there were shapes moving. Dark, shadowy figures. And everything was beginning to go cold … far too cold. With a gasp, Tonks realised exactly what was coming on board the train. Dementors! And she had only ever mastered the repelling charm once, and that was a long time ago. But how could she use it now, in front of these three kids? She'd blow her cover for sure! The cabin door slid open, and Tonks felt the Dementor's focus on her. It knew she was more mature than the others. She had no idea how – but it knew.

All thoughts of her cover went out the window: Tonks drew her wand and focussed on a happy memory, but she was damned if she could remember the incantation … expect … expect … come on! she shouted at herself, as she saw Harry fading before her. But now her own memories were overcoming her – as the most powerful witch in the room, the Dementor was focussing its energies on her more than the others. And nothing stood between her and it …

Remus! The thought sprung into her mind out of nowhere.

"Remus!!" she screamed with all the strength she could muster – forget the looks Ron and Hermione were shooting her: Harry was now officially passed out, and she needed help.

"Remus!!!!" Again, nothing.

She cast around her memories, trying to think of something; anything that might get his attention. Curse him for being such a sound sleeper! He used to babysit her with Sirius – they had run around in the garden together, Remus throwing the Frisbee for Sirius in his dog form … dog! He had been a dog, called Padfoot, and Remus was …

"Moony!!"

As she lost all control of her emotions, she vaguely saw a silvery shape leaping in front of her, as a loud, commanding voice said firmly and clearly:

"Expecto Patronum!"

The Dementor disappeared; the silvery mass faded; and everything else went black, as Tonks swooned on the floor of the train.

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A/N: I know some of this lacks continuity. Too bad. I made it up. That's why it's fanfiction. If you read it, you must have an opinion. The blue box and I would like to know. Thanks:D