I believe I am the Potions master at this school

This vignette isn't part of the seven part series that starts with "Why Snape never eats here" – it's just a reflection on what Filch, Lockhart and Snape were thinking the night that Mrs Norris was Petrified. However, if you read the series you will get a better feel for the particular version of the Potterverse in which the story is set.

There's nothing earth-shattering in this, just a little fun with a couple of minor characters.

Chapter 1: Argus Filch

He doesn't normally eat in the Great Hall with the teaching staff and the students, he normally eats in the kitchen with the house elves or takes a snack in his office – fried fish with chips is his favourite, and Mrs Norris always has a bite of the fish, she always has a little something from his plate to be companionable. But Halloween and Christmas feasts are an exception to the rule, so tonight he's put on an old and rather mouldy looking tail coat and joined the professors for dinner. You can't have a cat at the High Table so Mrs Norris has gone her own ways, patrolling the corridors, keeping an eye out for mischief ... she'll fetch him quick as a wink if Peeves or a student is up to no good, that cat is as smart as whip, she can almost talk, and she keeps an eye on that Hagrid when he comes up to the castle, too.

Hagrid! Hagrid shares his ambiguous status, not a professor but a member of staff, and not a qualified wizard, either, but he's not friends with Hagrid, definitely not. They're oil and water really, though they both have their shameful secrets - Hagrid was expelled from Hogwarts in his third year and they broke Hagrid's wand, but he never attended Hogwarts as a student at all, and that's worse ... much, much worse. And he knows very well what Hagrid keeps hidden in that pink umbrella – and how he gets his pumpkins to grow so big for Halloween. Hagrid might have to ask the Headmaster's permission before he can put a charm around the hen coop, but at least he can cast a charm, and that's a bitter pill to swallow, it's bitter to think that the half-breed lump can cast a charm, and he can't. No, he can't levitate so much as a feather, he can't use Evanesco or Scourify or any of a dozen useful little cleaning spells that would make his life so much easier, even though he's the son of a long line of pureblood wizards and witches and he should have been Sorted into Slytherin.

Yes, he should have been Sorted into Slytherin, and he hasn't forgotten where his House loyalties lie, even though he's a disgrace to his family, even though if the students were to discover his secret the Slytherins would despise him even more than the other Houses. He remembers the conversations in hushed voices when the adults thought he wasn't listening, he remembers the trials his parents put him through - he'd been dangled out of windows and thrown off jetties and pushed onto broomsticks, and nothing had come of it save a few broken bones and, on one occasion, a three day stretch in St Mungo's. He remembers the shouting and the tears on the day that his parents finally accepted that he had no magic, the day the rejection letter came from Hogwarts, because he'd had his name down there from the day that he was born. His father had accused his mother of having an affair with a Muggle, had said he's no son of mine - and then his father had walked out of the house and not come back for a week.

He'd been lucky, really, he could have been sent to live with Muggles, but his parents had been friendly with Professor Slughorn, and Slughorn had found a place for him as assistant to old Apollyon Pringle - and so he'd come to Hogwarts School of Witchcraft and Wizardry in his teens, though not as a student. But the position of caretaker of Hogwarts castle is at least respectable, and Hogsmeade is the only purely wizarding community in Britain, so he doesn't have to mix with Muggles.

Professor Flitwick is offering him treacle pudding, so he accepts a piece, and mumbles his thanks. The Professor is a very decent sort of a chap, hopelessly soft on the students of course – like most of the staff - but he really hasn't got that much to say to him, or to any of the teaching staff, he can hardly talk to them about how hard it is to get frog brains off a dungeon ceiling, that's a ladder job, that is - unless Professor Snape is in a good mood and has a moment to spare, and then it's just a couple of muttered words and a wave of the wand. Just a wave of the wand and all that muck cleared away – wouldn't that be bloody marvellous! So he'd dug out his father's old wand and sent away for that Kwikspell correspondence course, and he'd been very, very discreet – he'd taken a box at the Hogsmeade post office, he hadn't even risked having it delivered to the school, couldn't take a chance on a student finding out ... but now Potter knows.

He feels a bit sick at the thought, he really doesn't feel like filling up on rich puddings when Potter knows his secret, when Potter has probably told all of the Gryffindors, and if he's told the Gryffindors, it'll be all over the whole school in no time, and Merlin knows how the students might torment him when they know that he has no magic. Of course the students don't like him, they hate detention with him, they hate cleaning things, Muggle-style, without magic – but what do they know of hard work? They've got house elves to do all the cooking and the laundry and to tidy the common rooms and the dormitories, and they've got him to do all the swabbing and mopping and polishing. Oh, the students have an easy life here at Hogwarts, and from what he can see, their lessons are more like play – transfiguring raccoons, hurling cushions around the classroom, making bangs and explosions and brightly coloured smoke ... and Potter is the Boy Who Lived, he's a celebrity, he wouldn't have to lift a finger when he's at home either, even if he does live with Muggles.

Surreptitiously, he looks over towards the Gryffindor table but he can't see Potter or his two friends, the youngest Weasley boy and the Muggle-born Granger girl, where could they be? Students don't usually miss a feast, even Fred and George Weasley would rather stuff themselves at a banquet than make mischief, so what are they up to? And Potter is a horrid, sneaking little beast, he's been breaking rules from the very beginning ... last year he'd caught Potter and Weasley trying to break into the third floor corridor on the very first day of classes, and then he'd found them up the Astronomy Tower with Granger, at one o'clock in the morning - and that was some kind of a nasty prank, trying to get young Draco Malfoy into trouble, a bit like the pranks Potter's father and his gang used to play on Professor Snape.

James Potter and his best friend, Sirius Black, they'd been quite the double act, the leaders of their little gang ... what did they call themselves, the Marauders? They'd made his life a misery, they'd been worse than the Weasley twins, Dungbombs and Fanged Frisbees hadn't been the half of it, the horrible little bastards could get away with absolute murder. Professor McGonagall had a blind spot the size of a Hungarian Horntail for her star Quidditch player and her star Transfiguration student – and they almost always served their detentions with Hagrid, not with him, so he'd hardly ever had the chance to set them some cleaning work, Muggle-style, scrubbing the bedpans in the Hospital Wing or polishing a few suits of armour, some of the less co-operative ones ...

Young Severus Snape usually served detention with him – and Snape had plenty of detentions, too, but he'd felt a bit sorry for Snape, which was pretty unusual, he mostly loathed students, or at least the kind of students who earned themselves detentions, but as Snape's detentions were almost always for hexing the Marauders he'd gone easy on Snape. He'd mostly got him to copy out old disciplinary records or tidy his filing cabinets, little make-work jobs like that, and a good thing, too, because only a couple of years after Snape graduated from Hogwarts, he'd returned – as Professor Snape, Potions master. He'd been a bit nervous of Professor Snape at first, but the Professor didn't seem to hold all those detentions against him, not that he tolerates any familiarity, it's "sir" or "Professor" at all times.

Now Professor Flitwick is saying something about the troll that disrupted last year's Halloween feast, appalling mess it made in that girls' toilet, and who had to clean it up? And what a pity it wasn't Moaning Myrtle's toilet, because if it had been, he might have been able to persuade the Headmaster to close it off, let him put up a permanent "Out of Order" sign, and cut off the water supply – and that would have cooked her goose, the little cow, stopped her from causing a flood in the corridor whenever she gets into a snit. Then he remembers that Potter was involved in that incident, too, and he thinks, Potter can't keep out of trouble, there was that mysterious business with Professor Quirrell at the end of last year, supposedly Quirrell was a Dark wizard and he'd been after some treasure kept at the school, and Quirrell had ended up dead, a strange business alright ... and it makes you wonder, doesn't it, what Potter might be capable of? After all, Potter saw off He Who Must Not Be Named when he was only a baby, and that must have taken powerful magic, very powerful magic, and who knows what kind of powerful magic? But the Headmaster has a soft spot for Potter, because Potter and Weasley weren't expelled for that business with the flying car at the start of term, they got off with a warning and a detention, and Professor Snape wasn't happy about that, was he?

He glances down the table towards Professor Snape, and notices with some surprise that the Professor is also looking towards the Gryffindor table, frowning slightly, has he noticed that Potter and his friends are missing from the feast? But if they were up to no good, Mrs Norris would have reported to him ... and he thinks, my sweet, you're like another pair of eyes and another pair of hands, I don't know what I'd do without you! Oh, I know it's the dearest wish of half the student body to give you a kick but they wouldn't dare, and they wouldn't dare to hex you, either – I'd go straight to the Headmaster and he wouldn't stand for it, hexing a helpless animal ...

The feast is finally finished, and although it's been a good dinner he can't say that he's sorry that it's over, and the students pour out of the Great Hall, making a tremendous racket. It's well past their normal bed-time, and their normal bed-time is far too late in his opinion, anyway – students should either be at meals, in their classrooms or in their common rooms, allowing them so much free time to roam about unchecked is just inviting trouble – and he needs to do his rounds and find Mrs Norris before he can go to bed.

Aimlessly, he follows a gaggle of students up a flight of stairs, wondering why Mrs Norris hasn't materialised at his feet as she usually does, and he's starting to feel more than a prickle of anxiety because where can she be? Mrs Norris is so much more than a pet, so much more than a cat, she's his friend, his best friend - to be frank, she's his only friend - and he'd expected her to be waiting for him at the door of the Great Hall. So where can she be?

Suddenly, the students' chatter and bustle stop, he can hear Draco Malfoy shouting something about enemies of the heir and Mudbloods, and he shoulders his way through the crowd to find out what's going on.

Daubed on the wall of the corridor, between two windows, in foot high letters, is a peculiar message.

THE CHAMBER OF SECRETS HAS BEEN OPENED.

ENEMIES OF THE HEIR, BEWARE.

He stares at the words in puzzlement, of course he knows what the Chamber of Secrets refers to, but Salazar Slytherin's secret chamber doesn't exist, there have been any number of searches for it, and he knows the castle back to front and inside out, and he's never found it - and while he might have missed something, Mrs Norris wouldn't ... and then he realises what the dark shadow hanging from the torch bracket below the writing is.

He shrieks, "My cat! My cat! What's happened to Mrs Norris?"

Then he recognises the three students standing alone in the middle of the passageway, standing next to the body of Mrs Norris, students with the unmistakable look of people who have just been cornered, students who look guilty.

Potter! Potter and his two hangers-on ... it must be Potter, it must be Potter who's killed his cat, and this isn't a joke, this isn't a prank, this is murder. The little monster has murdered Mrs Norris! And the Gryffindor has been cunning enough to think of a way to cover up his tracks, a way to put the blame on to the Slytherins, and it would have worked, too, if he hadn't been caught red-handed at the scene of the crime.

"You!" he screeches. "You! You've murdered my cat! You've killed her! I'll kill you! I'll - "

And he thinks, if I had a wand and I could use it, oh yes I'd kill him, I've heard of the curse that would do it, the Avada Kedavra ... but then he hears the Headmaster calling his name, and Dumbledore sweeps between him and Potter, detaches Mrs Norris from the torch bracket, lifts her down and cradles her in his arms.

"Come with me, Argus," says Dumbledore. "You too, Mr Potter, Mr Weasley, Miss Granger."

He thinks, the Headmaster knows it was them, he's on to them – and this means expulsion for the three of them, at the very least it's got to be expulsion for a crime like this. It should be whipping, it should be Azkaban – but at the very least it will be expulsion.

Professor Lockhart steps forward eagerly. "My office is nearest, Headmaster – just upstairs – feel free - "

Dumbledore thanks Lockhart, and they head towards the stairs, through the silent crowd that parts to let them pass, and he realises that Professor McGonagall and Professor Snape are following them. Professor McGonagall is the Deputy Headmistress and Head of Gryffindor, this is her business, too, and Professor Snape ... well, Professor McGonagall is getting on a bit and it's pretty obvious who the Headmaster depends on. Professor Snape is the Headmaster's right hand man, and one day he might be Headmaster himself, the first Slytherin Headmaster since Phineas Nigellus, and about time, too.

Professor Lockhart shows them into his office, lights the candles on his desk and stands back, and the Headmaster lays Mrs Norris on the polished surface of the desk. He begins examining her, the tip of his nose barely an inch from her fur, and his long fingers gently prodding and poking her. Professor McGonagall is bent almost as close, Professor Snape is standing back, half in shadow, and Professor Lockhart is hovering about, saying dreadful things about torture curses and hideous atrocities committed in Africa.

He wonders how Mrs Norris died and if it was painful, and maybe Potter did it Muggle-style, strangled or beat her ... and if he did, expulsion won't be enough, no it won't, and he'll take matters into his own hands if he has to. He slumps in a chair by the desk, sobbing, his face in his hands, but he can still hear the Headmaster muttering incantations under his breath, and then Dumbledore says, "She's not dead, Argus."

Not dead? But Mrs Norris must have been dead for hours, she's gone all stiff and horrible, and he's seen dead animals before, occasionally one of the students' pets dies - a cat or a rat or a toad – and it's his job to arrange with Hagrid to have it buried. Yes, he's seen dead bodies before, and after a couple of hours they go all stiff and cold and flattened, just like Mrs Norris.

"Not dead?" he chokes, looking through his fingers at Mrs Norris. "But why's she all – all stiff and frozen?"

"She has been Petrified," says Dumbledore. "But how, I cannot say."

Sweet Merlin, Mrs Norris isn't dead, she isn't dead ... but Petrified or dead, it doesn't make any difference, it's still Potter's fault.

"Ask him!" he shrieks, turning towards Potter.

"No second-year could have done this," says the Headmaster firmly. "It would take Dark Magic of the most advanced - "

And what makes the Headmaster so sure that Potter doesn't know Dark magic? Is Potter above suspicion just because he was Sorted into Gryffindor?

He's choking on it, but out it comes, the admission that he's a disgrace, a freak, a more disgusting aberration than even a Mud-blood.

"He did it, he did it!" he spits, his face purpling. "You saw what he wrote on the wall! He found – in my office – he knows I'm a – I'm a ... he knows I'm a Squib!"

"I never touched Mrs Norris!" protests Potter. "And I don't even know what a Squib is."

This bare-faced lie is enough to take his breath away, of course Potter had looked at that Kwikspell letter and he must know what it meant - and how he could have been so stupid as to leave that letter lying on his desk for Potter to find? But he'd had to leave the room, by the sound of that bang Peeves had really done some damage, but he'd been wrong about that wrecked Vanishing Cabinet, it wasn't much use without the other one of the pair and Dumbledore had just told him to get rid of it because it wasn't worth fixing.

"Rubbish!" he snarls. "He saw my Kwikspell letter!"

The Headmaster and Professor McGonagall are looking puzzled, as if they can't understand what his Kwikspell letter has got to do with it, but thank Merlin Professor Snape is speaking up, asking the right questions.

"If I might speak, Headmaster," says Professor Snape. "Potter and his friends may have simply been in the wrong place at the wrong time, but we do have a set of suspicious circumstances here. Why were they in the upstairs corridor at all? Why weren't they at the Halloween feast?"

The Gryffindors start yapping about the Gryffindor Ghost's Deathday Party, claiming that the ghosts can confirm that's where they were ...

"But why not join the feast afterwards?" asks Professor Snape. "Why go up that corridor?"

The Gryffindors look confused, and Potter babbles something about being tired and wanting to go to bed.

How can anyone be expected to believe this, when ghosts don't provide food fit for living people at their parties? The Weasley boy is claiming that they weren't hungry, but his rumbling stomach gives the lie to that. Oh, it's clear that the little swine are hiding something, they know something that they're not telling, and Professor Snape knows they're not being truthful, too. Professor Snape is suggesting that Potter should be taken off the Gryffindor Quidditch team until he's ready to be honest, but Professor McGonagall won't agree, she's saying there's no evidence at all that Potter has done anything wrong.

How can she say this, when Potter has been found at the scene of the crime, with no credible explanation of how he came to be there? When Potter is clearly lying?

The Headmaster looks at Potter, and says, "Innocent until proven guilty, Severus."

What's this nonsense, innocent until proven guilty? That might be all right in the Wizengamot, but this is a school – full of students, students who lie and cheat and sneak and befoul the castle ... students who should be presumed guilty until proven innocent. And there have been no points deducted, no detentions handed out, it's unbearable, it's an intolerable insult to Mrs Norris. Is she worth nothing, just because she's only a cat? Because she belongs to a Squib?

"My cat has been Petrified!" he shrieks. "I want to see some punishment!"

The Headmaster tries to soothe him, tries to calm him, tells him that when Professor Sprout's Mandrakes have reached their full size, a potion can be made that will revive Mrs Norris. He starts to relax a little, because they haven't invented a potion that Professor Snape can't brew, when Professor Lockhart butts in. "I'll make it, I must have done it a hundred times, I could whip up a Mandrake Restorative Draught in my sleep -"

"Excuse me," says Professor Snape icily, "but I believe I am the Potions master at this school."

There's an awkward silence, and then the Headmaster dismisses the Gryffindor brats.

He's heard that Professor Lockhart has stepped on the toes of every member of the staff, he's even managed to annoy Hagrid, but this is the first time he's actually seen it for himself. He even forgets Mrs Norris for a moment, because Professor Snape is looking absolutely murderous and he knows that it was only the presence of students that kept Professor Snape from saying something much, much stronger to Professor Lockhart.

The door bangs behind the departing brats, Professor Snape swings round on Professor Lockhart, but the Headmaster is raising his hand in warning – it's rare to see Dumbledore openly exerting his authority like this – and whatever the Professor was about to say, he thinks better of it, and without another word he turns on his heel and stalks out of the room.

Professor Lockhart is beaming at him, "Well, now we've got the problem with your cat sorted out, I think it's off to bed for all of us, don't you think? And don't worry, Filch, if Professor Snape runs into any problems with the Restorative Draught, I'm always happy to pass on my expertise to less able wizards."