Fic: "X Marks the Spot", for shadowclub

[springmod]

Title: X Marks the Spot
Author: leni_jess
Recipient: shadowclub
Rating: PG
Characters: Harry Potter, Minerva McGonagall, Argus Filch, Mrs Norris, Severus Snape, and, well, the whole Hogwarts deal, pretty much - allowing for the war.
Summary: Mrs Norris is "just an intelligent (and unpleasant) cat" (JKR), an ordinary cat, and Harry is the Hogwarts' assistant caretaker. Sort of. The Headmistress has a murder on her hands, and will call on anyone she can to solve it.
Author's notes: shadowclub asked for "a murder mystery taking place in Hogwarts". I tried to avoid angst, as requested, even if I couldn't provide the humour she might have liked. My fervent thanks to R for helping me resolve the nitty-gritty of why and how whodunnit (murder mystery not being my forte). Thanks also to the mods for their patience with my dilatoriness, and to K and V for actual, and most helpful, beta-reading.


X Marks the Spot

Fortunately, it was the Headmistress who found the body, rather than some student. (Given whose body it was, though, she would not have been surprised by raucous joy or even abuse of the corpse.) Perhaps it was just as fortunate that most of the younger students were in the Great Hall, attending a wet Saturday afternoon 'guest lecture' given by the Weasley twins, who were under strict instructions to limit their demonstrations to what was both safe and seemly. Filius and Severus were supervising.

This was not a natural death. The poor creature looked smaller than ever, her twisted limbs and hunched body cast up at the edge of the swamp Filius had kept for a souvenir.

Minerva McGonagall sighed, and transformed, to allow her cat's sense of smell, far more refined than her human form could call upon, to discover what it might. The cat mouth opened in an expression of disgust at the musty odour that overlaid the swamp's natural complex of smells, but there was nothing she could identify as a clue to the murderer's identity. The smell of death was plain, but not helpful.

The law might not call it murder - indeed, killing a cat was not even an offence in the wizarding world - but the Headmistress did. Legal offence or not, the act showed a cast of mind she found repulsive and probably dangerous. Mrs Norris had served Hogwarts faithfully, if unloved save by her Squib master, and Hogwarts had in turn sustained her for many years past the natural span of a creature that was not even part kneazle.

Staring at the corpse of the caretaker's only friend, it was natural to think of the assistant caretaker.

Minerva had neither time nor skills to resolve this threat to the school's peace, but her youngest staff-member did. Moreover, anything that kept him busy was good.

She returned to human form and spoke his name, calling on the speech-web he had helped to build for the staff - far simpler than finding a fireplace to send a Floo message to someone who might not be where one thought him to be.

She was startled, as she should not have been, when almost at once he appeared. (It had turned out to be simple enough to allow staff to Apparate within the school, and yet to continue to prevent all others from doing so. Hermione Granger must have been one of the few who could find a practical use for Arithmancy beyond laborious prediction. Harry's speech-web charm complex was based on the same concept of defining exclusive groups.)

"Harry!"

"Sorry, Minerva; you sounded worried."

She collected herself. "Yes. I'm glad you came direct." She stepped back and twitched her hand slightly to indicate Mrs Norris.

Harry wrinkled his nose, looking quite like cat-Minerva for a moment.

"Anyone would think there was a basilisk about."

"Surely someone drowned her?"

He shook his head, the wild locks flying around before draping untidily over his shoulders again.

"With her body in that contorted shape? That's not the position of a cat fighting off someone's hands, is it?" Minerva was obliged to agree. "I doubt it. And it's not as if she couldn't swim. Poison, maybe. I don't know if one can drown under Petrificus totalis?"

Harry didn't seem to expect a response. He knelt at the swamp's edge and took out his wand. Without moving or touching the corpse he ran it just above the flattened dust-coloured fur, dark with water.

"Dead," he said, unnecessarily, adding, "several hours. Before lunch, maybe. Can't tell anything else, and she feels very odd; I'll ask Snape to look at the body."

Minerva managed not to bite her lips in anxiety; in a Headmistress such a habit would leave her mouth permanently in need of healing charms.

Before lunch, everyone in the castle had been moving freely about. No doubt some of the older students, now studying feverishly for NEWTs, could swear to each others' whereabouts, and there might have been a few tied down in detentions... She could hardly dose the whole school populace with Veritaserum, not for the death of a cat. Parents and governors alike would protest vigorously, and the Ministry, more reasonable though it perforce was these days, would support them.

She hoped fervently that her more temperamental staff - Severus sprang to mind - were demonstrably innocent, but on weekends most of them seized the rare opportunity for a little isolation from each other and from the students.

"Can you pin it down more closely?"

"After we move her, maybe. Snape can help. I'd want him to check for poisons, anyway." Harry looked up for a moment, smiling ruefully. "And Filius can still identify lots more hexes than me."

Out of habit Minerva rolled her eyes at the distance Harry and Severus firmly set between them. Most of her staff said 'Severus' as naturally, if not as amiably, as they would say 'Filius' or 'Minerva'. However, it was an intimacy one had to take, rather than be granted, and Harry Potter had never chosen to take it, though they worked effectively enough together. Harry had forgiven Severus long ago for Albus Dumbledore's death, and Severus had almost forgiven Harry for being James's son, as well as acknowledging that it was more than blind luck that had enabled him to despatch Voldemort to oblivion. He also chose to use Harry's first name, uninvited as far as she knew.

Tucking his right hand into his robes, as he often did, Harry stood and pulled out his AutoQuill and a small Muggle notebook, muttering to it notes she did not try to make sense of. His reports later would be clear.

Minerva looked at the body again and wondered what her assistant caretaker saw, or learned from his wand, that was taking him so long to record. A pity she could not summon Filius and Severus now too, to add their initial ideas, but the school was better served by having them keep an eye on their guests, both of whom still had some cautious respect for those particular former teachers.

She was reluctant to summon Argus, though she should: his grief would be profound.

Then a hoarse scream in the distance made her wonder if she had somehow spoken to him anyway. "My sweet! Mrs Norris!"

Over the sound of stumbling footsteps on hard stone Harry said quietly, "Mr Filch knows."

Odd how as an adult Harry gave Argus the respect and consideration he had never given the caretaker as a student, even though she had explained firmly at the beginning that she wanted him to make himself useful in his nominal role as well as in his real one as a practical teacher of Defence. Without that change in Harry's attitude, however, Argus would have resented and feared him to an extent that would have made Harry's official appointment worse than a waste of time. Not everyone would want to work with Voldemort's destroyer, even without hostility between them; Harry and Minerva had both had ample proof of that.

"Is everyone in this place suddenly a diviner?" she demanded, in brief exasperation.

Something small and dull-coloured shot around the corner, its outlines blurred, but its motion so characteristic that Minerva knew it for a cat in terrified flight even before she identified it as a ghost.

"No," she said helplessly.

Animals didn't become ghosts. Though there were the Headless Hunt's horses.... Animals didn't reject moving on past Albus's 'next great adventure', except when they were tied to dead wizards or witches. That old tale of Mrs Norris being an Animagus trapped in cat form couldn't be true. Minerva herself had tested it more than once.

Harry went down on one knee, holding out his left hand. "Mrs Norris!"

Argus's voice in the distance echoed the name.

The ghost skidded to a halt, wailed as dreadfully as her owner, hesitated, then crept slowly forward, visibly trembling, claws extended, fur erect. The fur didn't look wet, Minerva noted absently, though it seemed to be darker than in life.

"Easy, girl," Harry murmured, patting his bent knee awkwardly with his useless right hand.

Mrs Norris's ghost crept up to him, then suddenly darted in to shelter beside Harry's knee. Harry ran a gentling hand above, rather than along, the spine. (Coming in contact with her would be like dipping his fingers in ice water, Minerva knew.) The erected fur subsided a little, and the back lifted slightly, as if she were inviting him to stroke her as in life.

Then the ghost's head turned to look at her corpse. She let out another ear-splitting shriek and bolted, around Harry, away from Minerva, and off down the corridor, back towards Argus Filch.

"Not good," Harry said dryly, and rose again.

"Why?" Minerva demanded.

Harry shrugged. "Maybe people aren't the only ones who feel that being murdered is unfinished business?"

Then Argus appeared, stumbling, crying, though he swiped uselessly at his face once he saw them.

"Where's my cat? What have you done to her?"

Minerva said gently, but firmly, "She's dead, Argus. Harry says someone killed her. He's going to look into it for us."

"Who, then? I'll kill the bastard! Whichever little weevil did it, I'll put him on the rack, tear his nails out with hot pliers, drown him in hot oil, boil his flesh off his bones! Let him see how he likes it!"

Argus wiped his nose on his sleeve, sobbed noisily once more, and collapsed to the floor between them as if his hamstrings had been cut, bending his head down until his face was hidden against his knees.

Minerva didn't touch him. The only touch he was used to was from his cat. She had noticed that, even after five years of working fairly successfully together, he didn't touch Harry and Harry didn't touch him.

On the other hand, Harry still shied from touch too. His visibly crippled right hand discouraged some (and of course everybody knew of it and how it had happened), whereas the more sensitive saw his immediate withdrawal from anything hinting at physical intimacy. The loss of a lover and a best friend might have something to do with that, and Hermione Granger's reaction to similar losses was not so different. She didn't have her familiar to comfort her, having lost him too, near war's end, but she seemed to be more at ease in her isolation. She had always been able to bury herself in research, heedless of ordinary social interactions.

Harry didn't have the intellectual stimulus of working for the Department of Mysteries to distract him. He made do with poking his nose into everything at Hogwarts that could be said to need fixing, in his role of Argus Filch's magic-enabled assistant. He gave that far more attention than Minerva had ever expected, but she wasn't sorry; Argus had not come well out of the war either. She was a little surprised that Harry seemed willing to try to fix Argus; ordinarily he stayed well away from staff personal troubles.

"Argus, she's gone, but we'll find who did it, right?" Harry hesitated a moment, and Minerva wasn't surprised at that when she heard what he said next. "She hasn't left you, though. Her ghost's here."

Argus muttered, voice shaky, "She's scared to death."

"She is now, but she'll get over it. She'll come back to you, and snuggle up and be comforted, if you just wait a bit." Minerva hoped he was right. However sympathetic she felt towards her caretaker's loss, she didn't want a hysterical cat flying around the school for the foreseeable future.

Harry added, "She'll feel better when we know who did it."

Minerva thought it a great pity that a cat's ghost couldn't talk; that might shorten the whole dreary business, even if Harry would still have to come up with independent proof before Minerva herself could act.

Argus lifted his head. More steadily he said, "She can't stay there," and before either of them could stop him had reached for the small body.

He fell forward, almost into the water. Only Harry's lightning-quick grasp of his shoulder kept him upright.

The caretaker braced himself and heaved the corpse up and cradled it against his breast, sitting back on his heels, heedless of the water running down his dun coat, shrugging Harry's grip off.

Argus's embrace didn't change the body at all. Minerva puzzled for a moment over how long it took the body of a small animal to be completely overtaken by rigour: far less time than for a human body, she supposed.

Then she saw Harry reach out to touch, and the way he stiffened. His hand explored the body, and at last cupped it under the thin belly, taking its weight.

He drew back, and left Argus to his futile caresses and whispers.

His voice was very low when he said, "She really is petrified. Turned to stone, I mean, not like the basilisk did to her before, or Hermione or Penelope. She'd have weighed, what, five pounds, maybe?"

Minerva nodded; Mrs Norris had been thin as well as small, wiry, with no fat on her slender bones.

"She weighs a lot more now. No wonder Argus nearly went on his nose. Even if she did drown, and had been put under Petrificus totalis first, that wouldn't have happened, would it?"

"I've never heard of it happening." After a moment she added, "Ask Severus."

"If it's a possible magical disaster, he'll know," Harry agreed, without malice.

"I don't know a spell that will literally turn a living creature to stone, and kill it too. You can transfigure not-living things, of course. Though the energy it takes to change coal to diamond, for example, makes it impractical, and trying something quite against nature, like lead to gold, would kill most wizards," Minerva told him.

"That should put most of the students out of the running, even if they can transfigure a raven to a writing-desk, if you need power as well as knowledge," Harry pointed out.

Minerva's breath soughed in deeply with her involuntary relief. It was true. A spell so esoteric would be known to few. She hadn't come across it, in all her studies of Transfiguration. She had certainly never taught her students anything that decisively removed the life force from a living creature, no matter what form it was transmuted to. And, as Harry said, that level of power was beyond rare.

If Harry hadn't met such a spell in the years of vicious hand-to-hand fighting, no holds barred on either side, against the dedicated protectors of Voldemort's Horcruxes, only wizards of Filius's or Severus's wide knowledge were likely to know of it.

So there was another well-schooled wizard about, who was powerful as well as ruthless. One who wasn't afraid of the Dark Arts. Remembering Tom Riddle, and his accomplishments at sixteen, however, reminded her not to exonerate the students completely, out of hand. Any tendencies in that direction needed suppressing at the start rather than when the wizarding world was on the brink of destruction.

Argus said hoarsely, "Potter! Put her back the way she should be!"

For a moment Minerva thought Harry was going to have to explain he couldn't resurrect the dead (though she had had occasion to wonder uneasily about that).

"Not yet, Argus."

"Why not?" It was aggressive rather than pleading.

"Because we need to know exactly what it was whoever did to her. She's stone now, and I want other people to see her, think about what might have happened."

"I want her decent," Argus snarled.

"She will be," Minerva soothed. "To find her murderer, though, Harry needs all the information he can get. It's not as if Mrs Norris can tell him."

She hoped not, really, in spite of her earlier wish for easy information. An animal's ghost was a bad enough novelty, without its acquiring the ability to speak.

Harry got up. "Come, Argus, let's take her to my office, where I can ask Professor Snape and Professor Flitwick what they think, in proper privacy."

Argus grudgingly accepted the compromise. If Harry had hoped to leave the corpse undisturbed until his colleagues could examine it in situ, it had been too late the moment Argus appeared. Harry didn't have to explicitly refuse to restore Mrs Norris to her natural state, and Argus didn't force him to do so.

As they went Minerva said quietly, "I'll send Filius and Severus to your office as soon as the lecture's over, Harry."

"Thanks." Harry hesitated a moment. "What about the ghost?"

Minerva sighed silently. The ghost had come to him, for a moment, but she suspected that Mrs Norris might come more easily to cat-Minerva.

"I'll track her down, and see if I can calm her," she agreed.

~~~***~~~
Not long before dinnertime Harry called Minerva on the speech-web, asking her to come to his office to hear what his colleagues had to say.

Minerva Apparated herself there, unwilling to waste energy on walking three flights and many corridors on what was already too long and too tiring a day.

She was relieved to see Argus was not present, and that what lay on an old towel on a side-table looked like a cat respectably sleeping in a natural coil, rather than a monument representing the terror of being overtaken by death.

Harry was at his desk, his shelves of Dark Arts texts behind him (well-warded, she knew).

Severus sat upright in his usual cushioned Windsor chair beside the desk. Minerva knew Severus preferred to work on their joint responsibility for teaching Defence Against the Dark Arts on Harry's ground, rather than in his own intensely private space. Hogwarts had no accredited Dark Arts teacher, and her device to avoid Tom's curse on the position worked. Harry or Severus, whoever was appropriate to the topic or task of the current lesson, made a show of just happening to wander in to the classroom. Students were easily amused, and still, after five years, thought that funny, though they didn't show it before Severus, at least.

Filius, not an habitué, was perched on a heap of larger books set on a stool. Harry got to his feet and wandlessly gestured up a comfortable reading chair for her.

Her Potions and Dark Arts Consultant spoke for all of them.

"We have convinced Potter that (a), one cannot drown under Petrificus totalis, and would not unless the spell was lifted and the body then pinned under water. And (b), that even a basilisk does not literally petrify its victims in killing them. If there were still a basilisk about.

"However, there is a hex both Filius and I were aware of, Petrus verum. It doesn't require the magical energy true Transfiguration requires, just the applied will needed by all major spells. It turns flesh to stone, and it kills instantly. We can identify nothing else that would have had that effect."

"Very well. So, a knowledgeable, strong, vicious and determined wizard."

"Or witch," Severus agreed.

"Why kill her? Unless for pure malice?"

Filius said regretfully, "Both Argus and Mrs Norris were - are ... unloved, and go - went, out of their way to invite resentment."

"Killing is an overreaction."

"And Avada Kedavra might be a more common response from someone strong, skilled and sufficiently alarmed to kill," Severus agreed.

"What, caught doing something, and too scared or stupid to realise a cat could hardly give them away?"

"She'd fetch Argus fast enough," Harry pointed out.

"Not so fast that someone with that skill and determination couldn't get away first, even if they couldn't Apparate," Minerva said.

Then she listened to the silence that fell as all four of them contemplated the spectre of a fellow staff member having killed Mrs Norris, whether from panic fear or from anger.

Harry cleared his throat. "We've been interviewing staff and students and drawing up timetables, too. Though - since she was stone, there wasn't much physical evidence we could use to decide when she might have died."

So much for the hope that most staff and students could be quickly proved innocent.

Minerva pressed, "No possibility that it was a poison, Severus?"

With no delicacy at all, Severus replied, "I've taken samples and analysed them. No." He confirmed that he had conducted a physical investigation by adding, "Since her breakfast - you know she shared Filch's, of a weekend - she's had a rat, and probably two or three moths. Digestion had hardly begun. Both Harry and Filch saw her chase the rat around and catch it. So did some students. That was late morning, about 11:30, Harry and Filch have agreed. No one noticed her chasing moths."

And no doubt it would have been Filius, or Harry, who carefully tidied up after Severus before calling Argus in.

"When was she last seen? That anyone will say?"

Harry answered, "Before lunch. Last reported stalking two second-year Gryffindors who, whatever they were up to, apparently gave it up when she did that. They fled from the second floor to Gryffindor Tower, and that's the last anyone saw of her."

Minerva asked, "Was anyone absent from lunch in the Great Hall?"

Filius replied, "A number of NEWTs and OWLs students, but almost all of them were with their fellows in the common rooms or the library."

All of the staff had been present, Minerva remembered, and had stayed to give formal welcome to (and keep watch over) the proprietors of Weasleys Wizarding Wheezes. They had arrived earlier, and been informally welcomed and taken to the Gryffindor common room by Minette Prewett, who had ambitions of joining the firm when she finished school. Fortunate that Prewetts were less given to public mischief than those particular Weasleys.

How lucky that Minerva had asked Severus as well as Filius to keep that watch; Severus had had no chance to disappear and leave himself open to suspicion. There was still that small span of time between the last sighting and lunchtime, though, for almost everybody. After what Severus said about Mrs Norris's last meal, she would have had to be dead by the time almost everyone was in the Great Hall.

"You don't think we're going to find who did it by establishing, what's-it-called, 'alibis', then?"

"Not unless we find out more about when it happened than we seem likely to," Harry agreed. Filius nodded, and Severus inclined his head slightly.

So. They were really at square one still, then, except for knowing how it had been done.

She realised there was another question. "What about where it happened? It would be easy enough to move her body - the swamp is out of the way, for most people - to delay its being found."

"So easy to track the movements of a stone," Harry muttered. "When you changed to your Animagus form you didn't discover anything in particular?"

"I could smell death, and -"

Severus interrupted. "Then she did die there." With his usual bluntness he explained, "Since she was stone from the moment of death, you weren't smelling bodily decay."

Minerva had ceased to be squeamish before she started at Hogwarts, but she objected, "Then what was I smelling? Death is quite distinctive, to a cat."

Harry asked, "Does a cat sense the absence of life, and call that sensation smell? Or sense the residue of the spell itself? That's a killing spell. I know I can tell when Avada Kedavra's been used to kill, though I don't think I smell it... Was it the cat, or the witch, who identified death? Or killing?"

His voice tapered off as he thought about that. They all thought about it.

The next ten minutes went in theoretical dispute between Filius and Severus, until the Headmistress asked, "Is this helping?"

Filius said cautiously, "You identified death. So she probably died there. And either fell into the swamp in dying, or was tossed there, dead. We can ask Remus Lupin, you know, if he'd come by tonight, see what he thinks about it. He's back from Dubrovnik, isn't he?"

He didn't have to say that Lupin had plenty of experience in using his wolf-enhanced senses in the wake of violence.

Another wait, while Harry used the Floo to speak with Lupin at Grimmauld Place, which Harry had gladly turned over to him years ago. When not acting as liaison between various werewolf groups and several governments, Lupin spent much of his time scouring the house clean of all association with the Black family. Report said he was winning, however slowly.

Lupin agreed to come at once.

Minerva rose, saying firmly, "Let me know when you get more information," and returned to her office and the paperwork waiting there. Most of it she dealt with summarily, as always, using a complex of charms to analyse and respond, if required, or to file, picking out only the few items she needed to consider carefully. She didn't feel obliged to imitate Albus by dealing with each item personally, however idiosyncratically; she didn't have that kind of all-knowing, all-mastering, totally-drive-you-round-the-bend persona to support.

It seemed to her that her investigators were not getting on very fast. This was going to be a headache, and a pain both in the gut, and, for anyone who felt for Argus, in the heart. No one but he, however, was likely to miss Mrs Norris.

~~~***~~~
In the morning it turned out that Remus Lupin had added nothing to their sum of knowledge. Harry was grumpy, and confined his conversation to requests for tea and for honey for his pancakes. He built a small tower, then let it soak into sogginess while making unenthused passes at it with knife and fork. Minerva was short of sleep, and had a mild headache consequent upon nightmares about the killing having been done by a student in spite of all their arguments pointing to a mature and experienced wizard.

Severus and Filius both went off, fairly thankfully, to encourage their Quidditch teams. Harry didn't go to the match. He had definitively turned down Minerva's initial suggestion that he be assistant Quidditch coach, when she tried to recruit him as clandestine teacher of Defence. She had wanted to supplement Severus's excellent grasp of theory with Harry's intuitive skill for teaching the practicum which Severus, she had to admit, lacked. It wasn't the last match of the season, so Minerva had no obligation to attend.

She retired to her office.

Harry retired to his.

No one had seen Argus.

So matters rested until lunchtime, when Mrs Norris raced into the hall, tail a bottlebrush of fury, with Argus panting after her, trying to coax her to a halt.

Minerva discarded the notion that the students would see nothing unusual about the death of a cat. A ghost cat was far more interesting than the real cat had ever been, and Mrs Norris in a patent state of terror looked like promising prey for anyone whom she had victimised in the past. The Headmistress halted Argus with a word, and the ghost with a spell. Then she read the school a brief but severe lecture on the penalties that would be associated with unkind teasing. She didn't say so, but everyone knew she meant both the caretaker and the ghost of his cat. While not everyone gave up the idea of a little spiteful amusement, most seemed to decide it would not be worth it.

When the students finally got back to their meals Minerva muttered to Filius, "Now, of course, they'll all tell their families, and I'll be swamped with queries about what Mrs Norris really was. She's been here long enough; all the parents of our present students will remember her."

"Servant of the castle," he said briefly.

"Yes," she agreed. "I wouldn't have thought that carried the privilege of choosing to be a ghost, though. Ah well. There'll be something else for them to get excited about next week.

"Harry!"

"Yes, Headmistress?"

"What do you plan to do next?"

Harry rolled his eyes at her, no doubt thinking that technically almost every member of the staff was still eligible to be the killer.

His answer was certainly meant to discourage curiosity, hers as much as anyone's. "Poke around."

"I shall come to your office at two for a report," she informed him.

Harry didn't look happy, but she didn't see why he should be, when she wasn't.

That would give her another opportunity to find Mrs Norris and try, yet again, to dispel her continuing terror. Perhaps cat-to-cat communication would achieve something.

~~~***~~~
When the Headmistress entered his office Harry said, "We interrupted you last night, when you were telling us what you smelled at the swamp in your cat form. We never went back to that. Was there anything besides death, Minerva?"

"A slight musty smell I couldn't place, that's all. The swamp has a wide range of aromas of its own: waterweeds, reeds, little fish, insects, rot, new growth in various stages..."

"Musty," Harry mused. "I smelled that too, but it was familiar. I think I associated it with Mrs Norris's corpse, but since she was stone she wouldn't have smelled of anything besides that and swamp water... I thought of Salazar's basilisk at the time, though this wasn't nearly as strong a whiff, but that's dead - and no offspring lurking in the Chamber side-passages, either, thank Merlin. Imagine a thousand years' worth, if basilisks could breed without mating!"

"Can anything?" Minerva allowed herself to be distracted momentarily.

"Jellyfish, amoebas, that kind of thing. Though the Muggle papers made quite a fuss about a Komodo dragon that managed it all by herself, in one of their zoos, last summer..."

"Muggles," she muttered dismissively.

Harry shrugged and got back to business. "Minerva, I had the Marauder's Map out this morning, and I've been down the 'secret' passages. The Map shows Animagi, and people in Invisibility Cloaks, but not every living creature. None of the castle's kneazles ever showed up, not even the ones that belonged to students, like Crookshanks, poor old boy, or Millicent's cat, though Mrs Norris did. But of course she was part of the place. I decided I wanted to have a good look around."

Remembering what had come along some of those passages in the last stages of the war, Minerva suppressed a shiver. Harry had faced the Inferi with her and the few people then in residence, not all of whom had got out alive. After it was all over, she had cleansed the navigable passages rigorously.

Once Harry was working for her, nominally a caretaker, she had set him to blocking the outside entrances to those passages magically as well as physically. Even after that experience of invasion, she had felt it unwise to block them off altogether, however. Passages were exits as well as entrances, and nowadays Minerva felt very strongly about having a private exit wherever possible.

"You didn't find anything?" If he had, he would have come to her.

"No. Some of them have been blocked since long before the war, of course; I remember Fred told me - well, it doesn't matter."

It was no surprise to Minerva that the Weasley twins were familiar with these of Hogwarts' secrets, if not with all.

"What else is there to do?"

"Nothing much, until Mrs Norris stops charging around like a firework on Muggleweed. I want to get Argus to coax her into remembering, if she can, where she was before... before. To take us there. And to backtrack herself. She's smart enough."

That took time.

Argus managed to quiet his pet for short periods, but inevitably something startled her and she fled. At least she no longer yowled piercingly every time she did so.

It was the following Saturday before Argus (with Harry keeping a careful observer's distance, and Minerva even further behind) was able to lead her back to the swamp and urge her to take them back to where she had been before she died.

Eventually Argus said, deeply frustrated, though he petted the ghost consolingly as best he could, "She just doesn't remember, Potter. She's too upset, still. Don't harass her."

"No," Harry said thoughtfully. "I don't think that's it, Mr Filch. I'm wondering if she doesn't remember because it didn't happen here. Can you get her to look about? Would she be able to retrace her route if she found something familiar?"

"She would," Argus said vigorously. The idea that it was ignorance, rather than distress, hampering the little ghost seemed to make him feel better. He couldn't have been thinking about premeditated murder, or about a killer who didn't hesitate to shift a dead body to throw investigators off the trail.

It took more time, but Minerva was as determined as Harry to be patient. It might be important, in the long run, that she witness Mrs Norris's recognition of her death scene.

When Minerva was thinking about the solace of a glass of island whisky, rather than tea, Mrs Norris decided to take the stairs down to the fourth floor. With the persistence of a hunting dog, rather than the distractibility of a cat, she quartered the corridors.

She let out the little half-voiced mew of a frightened cat, then she started to run.

The humans followed her as quietly and quickly as they could. Suddenly she stopped, looking at a mirror in dire need of cleaning. Minerva saw Harry start, but before she could ask him what was wrong he went up to the ghost cat and asked coaxingly, "Here, Mrs Norris? Just be patient, girl."

His left hand lifted to the mirror. In private like this Harry seldom bothered to use his wand for magic, any more than he used his voice, unless the task was unfamiliar.

The mirror slid to one side, revealing a passageway wide enough to admit two, and with a narrow vaulted stone roof.

The light Harry summoned also revealed that after a few feet in the passage was completely filled by stone blocks, some whole, many damaged, and some smashed to flinders by their fall.

Mrs Norris stepped daintily into the passage, then hissed in fright, her back going up. She retreated to shelter between Argus's legs, but after a moment responded to his coaxing and ventured out, to jump partway up the slope of rubble and lie down, though just for a moment. Then she backed off, hissing again.

Argus tried to pick her up and could not, but she was not hampered by her insubstantiality: she turned and leapt at him, crawling inside the breast of his coat.

"That's my brave darling, easy now," Argus muttered, running his hand down his coat instead of down hers. The coat bulged convincingly, as if she had settled further into it, welcoming his soothing strokes.

Harry gave a deep sigh.

"So we have the place. You agree, Mr Filch?"

"You know I do, Potter." Then Argus added grudgingly, "Thanks for keeping me up to it. I thought this was a waste of time, after the swamp had her so confused, but now she's here, she knows, that's plain. She's not confused now."

"Yes," Minerva agreed quietly.

Argus turned to her. "Can I take her away now, Headmistress? I can feel her shaking."

Minerva thought it as likely that what he felt were his own shudders at the persistent cold contact with a ghost, but she didn't correct him. Master and cat had been harrowed enough.

"You don't need her help now, Harry?"

"No. Thanks, Argus."

"Thank you, lad," Argus said, gruffly sincere.

Then he bustled off, talking to his cat about revenge, as if neither Minerva nor Harry existed.

"Now what?"

"Now, we find out who knows about this passage besides me, Remus, the Weasleys, and Hermione, of course. Most of the others who knew are dead." Harry paused a moment. "Snape knows them all, but if he killed her he had about two minutes to do it and get down to the Entrance Hall. No time to take her all the way up to the swamp, over in the east wing -"

"Professors may Apparate," Minerva reminded him, though she had no wish for Severus to be suspected. He still dealt badly with distrust, and he had proved himself, over and over.

To himself Harry murmured, "Why would someone turn her to stone instead of just using, say, Petrificus and a quick Obliviate? Why kill her? Or if they didn't care either way, why take her body to the swamp? They could have left her here safely enough."

"You would have found her when you searched the passages - you did look in here, didn't you?"

Harry nodded, still looking distracted.

"So," she prompted, "whoever killed her didn't just want to conceal where they'd done it; they didn't want anyone paying attention to this particular place."

"Mmh, mmh."

If Harry had retreated into wordlessness there was no point in pressing him for more information now.

His employer took his elbow and led him out of the passage, then said with conspicuous patience, "Close the entry, Harry, before a student comes by."

Harry started, then did that.

He came with her to her office, and followed her in, but then he stood in the middle of the floor staring abstractedly at the big stitchery on the wall that depicted her native glen.

Minerva snorted softly and summoned the whisky from its cupboard, and two glasses. Harry started again when she pressed a glass into his hands.

He blinked at the healthy portion, then took an appreciative mouthful. Only then did he move, and seat himself in one of the armchairs ranged around a coffee table.

Minerva let him drink the whisky in peace - by which time she had had a second, somewhat smaller, amount, drunk more slowly than her first.

When he set the glass down he asked, "Do we have any visitors today? There's no guest lecture until next Saturday, isn't that right? Tilden Toots to talk up Herbology?"

"'Make your fortune with three green thumbs'," she told him dryly. "Yes. Luna Lovegood is here, but you know that; Filius asked her to interview the NEWT level students who might want to work for the press."

Harry smiled faintly. "If Luna doesn't put them off, they're tough enough to take the Prophet too."

"Having an alternative press does no harm at all," Minerva said crisply.

'The more the better," Harry agreed. "The people who write for Mr Lovegood at least have manners, though they're just as persistent as the Daily Prophet reporters. Anyone else?"

"There are always some family members visiting children," Minerva pointed out.

"Is there a list made each time of who's come, when they come, when they go?" Harry asked, heavily patient.

"Certainly," Minerva answered primly. She snapped her fingers, and a small roll of parchment leapt from a corner of her desk.

"Is that going to be accurate?"

"You aren't the only one capable of security charm work, Harry Potter. It's maintained automatically - and I transfer all past lists to the permanent journal, too."

"Yes, Headmistress," Harry said meekly, and reached for the scroll.

He read it and sighed, then got up. "I did wonder. Thanks."

He left without saying more.

Minerva looked at the door closing silently behind him, then read through the list herself, checking it against last week's list in the journal.

Parents of younger children in each of the houses, none of whom had been here last week. Older brothers and sisters and some cousins, many of whom lived in Scotland and found it easy to visit regularly, and to take siblings out on Hogsmeade weekends.

The Muggle Studies Professor's fiancée. Irritating woman, but with any luck she would drag him away from Hogwarts and Minerva could appoint the candidate she had fancied for some years now.

Neville and Susan Longbottom visiting Professor Sprout: not unusual. Hard to tell which helped the other more, these days. Minerva suspected that Pomona might be retiring to Lancashire one fine day, to amuse herself in Neville's greenhouses.

Draco Malfoy, now a governor of the school, which was ridiculous at his age, but he did it conscientiously. Some public recognition of his war service had seemed to her and several of the other governors to be appropriate. Undoubtedly talking with Slytherins, he was Severus's object lesson in not swallowing pureblood propaganda. Also Marcus Flint, not a governor, but as much an object lesson as Draco. At least Marcus was married, and attached to his wife, as well. About time Draco and Su Li did the same and made sure Draco's visits would be gossip-free; war wounds or not, he was far too good-looking, in that distinctively colourless Malfoy way, to go untrammelled through a host of idiot schoolgirls.

Nothing there. She ran her eye down the list again, and her heart sank, as she saw what Harry had sighed over. Then she fought down her fury.

She refrained from pouring herself another whisky, and walked briskly over to her desk to bury her fear and fury in work, refusing to speculate on the whys of it.

~~~***~~~
Minerva remained in her office for perhaps another hour, undisturbed save by a Floo call from the Ministry, before she heard Harry's voice, low, urgent: "Minerva! Come to me now!"

She tossed aside the piece of special pleading she had been reading, and Apparated straight from her chair, homing in on Harry's presence.

Her wand was out, but he didn't need assistance. She wasn't surprised to find him in the fourth floor corridor by the dirty mirror, the passage open, and in its entrance the Weasley twins standing, trying to project nonchalance. George, at least, had a faint crease of impending worry between his eyebrows. (It was simple to distinguish them these days, with the scar Percy had given George a sharp white line down his right cheek.)

Mrs Norris's ghost darted from Harry's side to leap up at Fred, claws out; he fended her off with a threatening gesture, though he didn't go for his wand. She retreated, hissing, fluffing up. None of them, except Harry, could be as self-confident as they tried to appear.

"Headmistress," Harry said without looking at her. "George and Fred are about to explain to me why they found it necessary to kill Mrs Norris, and why I found them, today, attempting to confine her within the mirror passage."

Trust the Weasleys to find out how to compel a ghost to stay where it had been killed. At least Myrtle had the run of the lake as well as the disused toilets.

"We didn't kill her -"

"Just made her stone -"

Harry was looking almost as stony as Mrs Norris had been. These men, after all, had been friends of his - of a sort - for most of his life.

Fred said, rather pettishly, "She was in the way."

"So you stamped on her."

"No," George denied quickly.

"We were trying to confine the basilisk, but -"

"Fred!" George sounded horrified. So they hadn't intended full confession.

Minerva decided they should be questioned separately. She was resigned to not being truly astonished that, with the Weasleys in the mix, there was also a 5X Ministry classification dangerous magical animal. She hoped Harry could deal with it promptly, wherever it was. If it was behind that tumble of stone, well and good. If not, the sooner the twins were separated, locked away, and had the truth gouged out of them, the better for her school.

How had they managed to progress from the thoughtless malice of Canary Creams and Ton-Tongue Toffees to letting a basilisk loose in a school? Imperturbable selfishness, she supposed.

She rapped out, "Where is this basilisk?"

George eyed her dubiously. He knew his former Head of House under the influence of righteous anger. So did Fred, and Fred weakened first.

"It was supposed to be in the Chamber of Secrets, you know, old Salazar's place, that Harry found," he babbled nervously, "but we couldn't get in!" With an evidently genuine sense of grievance he added, "Dumbledore must have barred it even more strictly after we left school."

"Good," Minerva said grimly, knowing perfectly well what Albus had done to ensure that the Chamber, with its potential for disaster in yet-undiscovered secrets, was inaccessible.

"So we thought, well, this passage is blocked, but the roof and walls aren't down all the way in, there's a stretch you can get to, and we reckoned -"

George seemed to realise Minerva was looking less rather than more satisfied with the explanations tumbling out. He said quickly, "It's only a little one, hasn't even a hint of its red plume yet, just a baby. It can't get out."

Later on she would find out whether they had come by the young basilisk by chance, or whether they had deliberately bred it by setting a toad to hatch a chicken's egg, as Herpo the Foul had done. And what, precisely, they intended to do with it. She could see the point of using Hogwarts as its cage, however much she deplored it.

George probably wasn't lying.

"Come with me," she snapped. "Now. Harry."

"Yes, Headmistress?" If he wasn't protesting, he agreed with her.

"Find it and destroy it," she said between her teeth. "Not alone. Get Professor Snape to help you."

"No!" Fred protested. "After all our trouble -"

"You're in more trouble than before, Mr Weasley, both of you. Not just with me. You did look up all the international laws you were breaking, didn't you, by not handing the basilisk over to the Department for the Regulation and Control of Magical Creatures for destruction?"

"But a basilisk!" Fred protested. "We're going to use it to become Parselmouths. We've got it all worked out. It's not just inheritable, you know!"

George chimed in, unable to hold back from one of their head-turning conversations. "Harry didn't inherit knowing how to talk to snakes. We have the process almost right, we're sure."

Fred said eagerly, distracted by the thought of another Wheeze almost in reach, "It'll work once the basilisk is mature, and it'd be safe enough here, no one would find it. We'd have lots of customers - think how many wizards would love to be able to talk to snakes! Before you know it no one would think being a Parselmouth a sign of a Dark Wizard. See, Harry, you'd benefit too -"

Fred Weasley would still be babbling when the Aurors came to throw him to the Dementors, Minerva thought.

Harry asked scathingly, "Are you out of your minds, both of you?"

"No, Harry," George said winningly, "we wanted to improve your investment earnings for you -"

Harry snarled, even as Fred said placatingly, "We've done well by you, Harry, admit it -"

"You've done just what you fancied," Harry retorted, "without regard for anyone's safety, and without asking me if I wanted to be done well by a basilisk! Shut up, both of you, before I hex you tongueless!"

They looked genuinely taken aback by that rejection.

Minerva seized the moment. "Come along. Gentlemen. Harry, you can manage?"

"Professor Snape will be free by now; I'll call him up."

He rounded on Fred. "What spell did you use to make sure the basilisk couldn't get past the stones you must have tunnelled through, to get it to its pen?"

"Convinced it that all the walls are solid - ceiling and floor as well, since it's small enough to climb the rubble to the top. All it sees is the box it lives in. It won't know where the rats and mice and spiders come from."

"Not for much longer." He added with some malice, "If you knew how limited the conversation of most snakes was, you wouldn't be in such a hurry to become Parselmouths. They're not all Nagini."

Minerva tapped George's shoulder, and he and his brother followed her, all the way back to her office, and on to a little-known holding cell for serious malfeasants. She threw up a temporary stone wall across its middle and left them to think over what they had done. Even they could hardly imagine they could talk their way out of this. A few hours' isolation from each other would make them very uneasy, she knew from experience. While they were stewing she would make and duplicate a careful pensieve record. Harry and Severus could add their dealings with the basilisk to it later.

There would be time enough to get to what exactly had killed Mrs Norris, though they had essentially confessed already that she had died to protect their nasty secret.

~~~***~~~
With more difficulty than before Minerva returned to the eternal administrative duties of the Headmistress of the only wizarding school in Britain. Two small Pensieves now rested (separately) in her secure storage.

Eventually Harry and Severus showed up. Harry's left forearm was newly bandaged, but in response to her horrified query he said, "No, it didn't bite me. That was a scrape from a snapped-off scale, during its death throes. Poppy checked very carefully, Minerva, I promise you!"

"For such a little thing," Severus commented, holding his hands less than a foot apart to indicate how small, "it threw an almighty tantrum at being killed."

"You took no damage, Severus?"

"Nothing more than some tears in my robes that the house-elves can easily repair." He added when she frowned, "It was too young to produce venom. That's probably what our ingenious inventors were waiting for. Lucky that Harry found out what was going on now, rather than a little later."

Harry explained, "Snape thinks they put a forced growth charm on it."

Minerva sighed. "We'll find out. Harry, there was only one, wasn't there? I haven't tried to question them yet."

Harry said rather dryly, "Snape doesn't believe in taking anyone's word for anything. We made sure."

Well, that was something they had in common these days. A pity that the war should have pushed Harry towards Severus's level of distrust, rather than peace allowing Severus to experiment with having confidence in another. But what else could one expect, with the wizarding world the way it was, had been for centuries?

"Have you spoken to the Aurors, Minerva?" Severus asked.

She shook her head. "This is my school; I'll get to the bottom of this. Then I'll hand them over. There's no more than civil penalties, unfortunately, nowadays, and I suspect Weasleys Wizarding Wheezes is financially secure. They've been able to open the second shop in Hogsmeade in Zonko's old premises, after all."

"They haven't gone out as much on a limb in opening that as they did with the Diagon Alley shop," Harry agreed.

Severus said thoughtfully, smiling, "What might make them sorrier in the long run than Ministry fines, Minerva, would be if you banned Hogwarts students from the Hogsmeade shop. You are quite entitled to do that, and of course to enforce it magically."

Minerva smiled too, vengefully. It would be a long time before she forgave the Weasley twins, and she doubted if she would ever trust their good sense or good will again. A joke shop wasn't in the same class as Mrs Porter's Home for Wayward Girls, or Quentin Questin's shop for betting on Muggle horse races (or anything else whose outcomes could be skewed by magic). There was even a thriving business in illegal experimental animals in the back rooms of the newest pub (which had a remarkable security system; Auror raids had never yet found any prosecutable evidence of wrong-doing).

The joke shop proprietors, however, were quite as dangerous.

She would take that suggestion.

After getting Harry's full report on his pursuit of the twins, Minerva asked, "Is it too early to have them out?"

Harry hesitated.

Severus shook his head. "Let them sweat. It's lunchtime."

Harry offered, "Mrs Norris seems to be happier now. I think she knew the basilisk was there. She enjoyed trying to worry the corpse. I haven't spoken to Mr Filch, Headmistress; I thought you'd want to do that."

"Yes," she agreed, and rose. "Come, then. I suppose we'll need to see if Miss Prewett knew about any of this, too."

"They're quite security-conscious," Harry commented.

"For their own secrets, if for nothing else," Minerva agreed dryly.

~~~***~~~
It became evident that the twins had decided to brazen out a full confession, with almost as many justifications as they had tried to bring to bear that morning.

Mrs Norris had been killed by the basilisk. She had surprised the twins taking it from their bag of Wheezes brought for the lecture the previous week.

They had slipped away from their cousin Minette when a first year had needed her attention. They knew where they were going; they had made a temporary way through the fallen masonry on a previous visit. It would have taken only minutes to hide their basilisk and charm it into belief in impenetrable prison walls... save that the caretaker's cat knew them of old, by scent and by mischief, and had come upon them at quite the wrong moment. Her instant attack had pulled free the blindfold that covered the creature's killing gaze.

Petrification by a basilisk being readily identifiable, the twins had decided to cover their tracks with Petrus verum and directing attention to the swamp rather than to the blocked secret passage. Minerva did wonder what secret vanity led them to leave the corpse at a place they had created: even more their own than the hidden passage.

Word of the ghost cat had travelled across wizarding Britain with the usual speed of fascinating anomalies, and the Weasley family still had a close line on the gossip of the wizarding world. The twins had been horrified. Mrs Norris would be certain to find her death place eventually, and to betray their secret to anyone who cared to pay attention. It hadn't taken them long to research the process for confining a ghost, and they had determined to shut Mrs Norris up with her killer as soon as they might. Offering Minette a job in the Hogsmeade shop had been the obvious reason to return.

Such a pity that Harry had guessed they had come back for something else.

He said thoughtfully, after they had been seen back to the holding cell, "Muggle detective novels, you know, often go on about murderers betraying themselves by returning to the scene of the crime to cover up just a little bit more carefully."

Minerva shrugged. "So they're not murderers after all," she conceded. "They're banned from Hogwarts just as our students will be banned from their shop. And I hope," she added testily, "that Miss Prewett will have more sense than to ask them for a job in Diagon Alley to replace the one she's not going to get in Hogsmeade!"

~~~***~~~
Some weeks later Harry observed, "Hermione thinks Mr Filch needs a new cat. A proper kneazle. She plans to ask one of the wizards at the British Museum - they have tribes of both cats and kneazles - and just bring it to him."

Minerva asked dryly, "Has she acquired a replacement for Crookshanks yet?"

Harry responded as dryly. "After how many years? No, she hasn't. I told her to forget it. If he asks, then yes, but otherwise..." He shrugged, and said very quietly, "He's not ever going to lose her now."

The Headmistress briefly contemplated the probability that some day in the distant but foreseeable future she would have the ghost of a Squib caretaker infesting Hogwarts, as well as his cat. If you had the one, you'd have the other. Then she too shrugged. Hogwarts was used to ghosts; they were all servants of the castle, in the end.

~~~***~~~
Eventually Mrs Porter took over Zonko's old shop and branched out into selling scented (and charmed, of course) candles and oils and other sensual delights for the curious and open-minded. The twins' milder line in such items had been quite successful in the short time they had operated in Hogsmeade.

Her potions maker, however, drew the line at producing Amortentia for open sale. He pointed out that it would do her business no good if the Headmistress banned Hogwarts students from a shop that might otherwise do quite well from older students as well as from adult residents of the village. Leaving some things to nature, he said, was a better way of doing business. Most witches and wizards were sufficiently interested in their own profit and pleasure to take small chances, if not big ones.

~~~The End~~~