C/O 221B Baker Street, Muggle London (Book 1, pt. 5)

[one_windiga]

Title: C/O 221B Baker Street, Muggle London
Fandom: BBC Sherlock
Pairing: Sherlock/John
Rating: PG
Prompt: John and Sherlock are forced to adopt a 7-year-old Harry Potter.
Other: written for an anon for the Sherlock kinkmeme. You can find the original prompt and fill here.

Previous part.

Of course, once he was back in the castle, he immediately had to tell Theo, Ron, and Hermione about it. The three of them were awed by it, especially Theo, who said his older brother had spent three months trying to charm a cloak invisible, with no success. He suggested reading the quiz keys in the professors’ offices with it, an idea that Hermione quickly shot down, much to Ron’s disappointment. Harry sided with her, and since it was his cloak, the other boys had to accept it.

Still, they were all happy to use it to sneak around the castle after hours to avoid getting caught by the prefects and docked points for breaking curfew. After a few late-night excursions, bumbling about squished together under the cloak, they finally settled on the Quidditch pitch as their Spot. At the sort of late hours they were sneaking out, there was nobody using it anyway, and it was far enough from the castle that they could be reasonably louder - and visible - and still not risk detection. As long as they could get out there safely, it was a fair bet that they would be golden once they hit the grass on the pitch.

Not to mention that it was surpassingly comfortable to spread the cloak out on the grass and lie back on it, gazing at the stars while they chattered. Sometimes they would bring their homework out with them to get a minute of peace and quiet away from the other students. Other nights, Harry and the boys would break into the broom shed under the disapproving eye of Hermione and fly loops around the pitch lazily, brushing each other’s broomtails as a bit of a challenge before zooming off. There were apples and cheese and bread and tarts, whatever they could smuggle out of the castle, and inevitably it would all be eaten, no matter how many declared themselves still stuffed from dinner. It was good fun, the lazy kind of fun that left them smiling through their yawns as they brushed the grass off their knees and stumbled back into bed.

But that didn’t mean that Harry was spending all of his free time lazing about the grounds. The nights they spent at the pitch were wonderful, relaxing breaks from his detective work. After all, he had already solved the mystery that was Professor Snape. And then he’d gone on Christmas break, and now that he was back… well, Hogwarts was just full of surprises, wasn’t it? He intended to figure out every last one of them before he graduated. Preferably before the end of his first year, if he had his way, but there was no point in getting ahead of himself.

The first order of business was to figure out this nonsense about the third floor wing that Dumbledore had said was off limits. Harry had learned, through the mysteries he’d seen Sherlock solve, that nearly all the times someone told him not to investigate something, that something was the most in need of investigation. Either that, or they were exceedingly clever and trying to plant a red herring, but Harry didn’t think Dumbledore was being quite that cunning. He was, after all, a Slytherin, and Dumbledore was most definitely not. Cunning was not Dumbledore’s usual mode of operations.

So whenever Harry had the chance, he would pull out the invisibility cloak and go wandering up to the third floor. He tried to do it on off moments when the halls wouldn’t be crammed with students that would make it difficult to slip through without being jostled and noticed. That meant that he could only do a room or two at a time, but he was making progress, even slowly, and narrowing down rooms as he went. There had to be something interesting in there, probably something dangerous, but surely something important, that Dumbledore didn’t want getting out.

What better reason was there for Harry to find it?

After hunting through seven of the rooms - going in a very methodical, orderly fashion, of course - Harry finally stumbled upon one that was locked rather more sturdily than the others. Sherlock had taught him to pick locks as a matter of course, but this appeared to be locked magically rather than by use of an actual locking mechanism. A simple alohamora charm did the trick, though.

Keeping his wand out, he pushed open the door slowly, poking his head through. He froze there for a moment in utter shock before sliding the rest of his body into the room. There was a giant three-headed dog inside, about the size of a small house. Its paws were crossed over a trap door in the floor, and its three heads were resting, bored, upon them, eyes half-closed.

Harry drew a breath. That was clearly a mistake. The dog instantly snapped into alertness, fixing its eyes on him and drawing back its lips to reveal three very large muzzles filled with very, very large teeth. It rose up slowly, and Harry swallowed as it began to growl, drool dripping onto the stone floor in heavy splatters.

“Nice doggy, nice-“

The closest head lunged at him, snapping its jaws inches in front of Harry. Harry gave up his mollifying words and stepped back into the hallway, slamming the door shut behind him. He felt the charm lock it automatically as he did, and he leaned back against it with wide eyes as the wood shuddered beneath the weight of the dog’s paws and jaws. He could hear its claws scraping shavings of wood away. It was only after several minutes of terrified silence that Harry regained his breath, then went running to find his friends.

Hermione was concerned with what exactly the dog was doing there in the first place. Theo wanted to know how they’d kept it a secret. Ron was mostly worried about whether it was likely to escape and go prowling around the castle. Harry was of course curious about all of the above, but found himself consistently driven back to the all-encompassing question of what exactly the dog was guarding beneath the trap door.

His solution, much to Ron’s dismay, was to bury himself in the library with Hermione and research. There was a giant three-headed dog in the castle. They hadn’t conjured it out of nowhere - at least, Harry didn’t think so; that was the sort of conjuring that was very difficult to cast in scale and complexity, and that would probably require a Ministry permit that he suspected didn’t exist. If it didn’t appear from thin air, then it had to have come from somewhere, and giant three-headed dogs tended not to escape notice in civilized societies, as far as Harry was aware. And if civilized society had noticed it, then it would be in the library.

Ron made a few disparaging comments about disappointment in the young generation, who volunteered to go about reading books and sticking their heads anywhere near the vicinity of a giant three-headed dog. After about an hour of interrupting the research with complaints, Harry grew rather impatient and asked if it would make him happier if there was only one head. Ron looked at him as if he’d offered to go swim into the lake and befriend the giant squid, before managing to get out that no, one head would not improve the situation, thank you very much.

Eventually they had dismissed Ron to go home when he’d fallen asleep on his books. Theo left a few hours later to meet with Professor Flitwick about the Charms homework. After a few days of burning the midnight oil to research, they finally hunted down a whiff of a trail in an old book written by a monk on the various forms of devil animals; from there they found a travel guide to Romania, and that led them to a cryptozoology tome that mentioned giant three-headed dogs, hellhounds, distantly related to the mythical Cerberus that was rumored to guard the mouth of Hell itself. The author dismissed the race entirely as conjecture, the stuff of gossip and whispers, completely baseless on fact. Harry muttered to himself and contemplated writing in an angry letter.

Still, at least now they had a start. They couldn’t make much progress, though, until they found something else that would give them a hint on how to subdue the beast - or at least avoid its jaws - long enough to get down the trapdoor. Harry had a few ideas on how to continue their research, but unfortunately, Hogwarts seemed to have other ideas.

Imbolc night, when Harry had planned to go and ask Professor Snape for a pass to the Restricted Section to get some more research clues, his plans were interrupted violently. Professor Quirrell came bursting into the Great Hall yammering about trolls and danger before fainting dead away on the ground. Harry stared at his prone body with no small amount of distaste. His parents would never faint like that, and they’d faced down worse things than trolls.

It wasn’t a surprise when the professors ordered the prefects to guide the students back to their common rooms. Harry tried to catch the eye of Hermione or Ron, but they had already disappeared into the crowd of Gryffindors on the opposite side of the Hall. It was all he could do to elbow his way over to Theo as they all made their way out of the giant doors.

“Theo!” he hissed.

Theo jerked around, casting a glance back to Harry before sidestepping a large older Hufflepuff. “Thought you’d got lost in the fray for a minute there!”

“No,” Harry said low, and grinned mischievously. “But I plan to.”

Theo blinked in confusion. “What- “ Harry grabbed his arm, yanking him out of the train of Slytherins. They slipped behind a suit of armor, then scampered out into the halls, away from the other students. In the melee, nobody noticed that they’d disappeared. “Harry, what are you doing?”

“This is the perfect chance! Nobody’s paying attention; we can go back to the hellhound’s room!”

There was a moment of distressed silence before Theo leaned in and rapped his knuckles against Harry’s forehead. “Why would we want to go back to the hellhound’s room, Harry?!”

“How else are we going to get more clues?”

“Oh my God, my best friend is a lunatic.”

Harry laughed. Theo seemed to take that as confirmation. “You think it’s exciting, I know it!”

“No, what I think is that you need to see Madame Pomfrey for the knock on the head you must have gotten!”

“That’s boring! Don’t you want to see a hellhound?”

“I also want to live to see tomorrow, and I’m not sure the hellhound’s up to giving me that.”

The noise of footsteps echoed down the hall, mature shoes echoing on the flagstones. Harry immediately narrowed his eyes. “We’ve got to go,” he whispered, “right now, or they’ll catch us.” With that, he grabbed Theo’s arm and grabbed him off, ignoring Theo’s groan of protest.

He charmed the door open when they reached it and, glancing around once to be sure the hallway was completely empty, slipped inside. To his surprise, the hellhound did not immediately start looming and growling as it did when Harry had first arrived. Instead, it was gnawing at a gigantic leg bone from some large animal, ripping the flesh from the bone and swallowing it down with gusto.

“Someone’s fed it,” Harry said wonderingly.

“Yes, I can see that. Now can we go before it decides that they didn’t feed it enough?”

“No, Theo, you don’t get it, that means it’s somebody in the castle that’s set him up to guard here. And it’s somebody that’s come to feed him themselves, or at least get the house elves to do it.”

Theo didn’t make any sudden moves for the door, but he also didn’t seem inclined to go any closer. Harry, on the other hand, took a few slow steps towards the dog. The animal, which had glanced up at their arrival and dismissed them in favor of its meat, stopped chewing when Harry was almost within arm’s length and began to growl, dropping his meat to draw back his lips from his impressive teeth.

“Harry, you’re too close!”

Theo grabbed the back of Harry’s shirt and tugged. Harry obediently took a swift step back, holding up his hands as if to declare himself harmless. The dog snarled softer, hackles lowering, until Harry had moved back to the door to stand next to Theo. Only then did it lower its head to return to its meal.

“Interesting. It isn’t angry at everyone, just people trying to get inside… It’s not a wild animal. It’s just a … really, really big guard dog. Someone taught it that.”

Crossing his arms over his chest, Theo frowned. “So someone in the castle raised a giant three-headed dog, put it in here, and has been feeding it the whole year?”

“And Dumbledore’s in on it. He’s the one that told us this wing’s off limits.” Harry hadn’t had the best impression of Dumbledore from the beginning, but his opinion of anyone that was keeping secrets from him was abysmal. Part of him recognized that, logically, Dumbledore hadn’t done this to keep secrets specifically from him, just to keep them secret in general. It didn’t make him feel any better.

Theo, like many of the other young Slytherins, was not nearly so brimming with affection for the headmaster as some of the other houses. He didn’t immediately deny the possibility, as Harry suspected Ron and Hermione would have. “Why would he want to do that?”

“I don’t know. But I’m going to find out.”

Theo sighed. “Is that a promise?”

“That’s a promise,” Harry said grimly, heading back out of the room.

By the time they got back to the Slytherin common room, all the students had been herded there already. The prefects were in a corner talking amongst themselves and didn’t notice Theo and Harry slip in. Draco, flanked by Crabbe and Goyle on the couch by the entrance, did.

“Where were you two? We’ve been stuck here almost an hour!”

Harry, momentarily taken aback, considered his options. Leaving out all mention of Fluffy, the third floor wing, or the trap door, he just mentioned the one part he thought Draco might be appeased by. “We’ve got some dirt on Dumbledore. We were hunting down some more proof.”

A malicious smile flickered onto Draco’s face. Harry had hit the nail on the head. “About time! My father says that barmy old man should have been removed from office years ago.”

And though he was more concerned with finding answers than getting to Dumbledore - after all, he couldn’t be sure yet whether the hellhound was guarding something bad or good - Harry played off of Draco’s concerns and held up his hand, his index and middle fingers crossed. Draco grinned wider.

“Don’t tell anyone we were out, yeah?” Theo said, taking advantage of Draco’s momentary appeasement.

“I suppose I don’t have to,” Draco drawled, trying to sound harder to convince than he was. Harry could see that the boy was already wishing them luck.

“Thanks,” he said, casting him a grateful smile.

Before Draco could reply, Pansy cast him a dark look from across the room, having just noticed who he was talking to. She raised her eyebrows significantly, and Draco shut his mouth with a click, looking away from both her and Harry. Harry sighed inwardly. Maybe that could be his project for next year, figuring out how to get Pansy and Blaise off of his case. He suspected some of the Slytherins who, like Draco, were caught up in the peer pressure, might ease off.

Still, there were bigger problems at the moment, like what the hellhound was guarding for Dumbledore. So instead of pushing the issue, Harry settled down by the fire with Theo so that the prefects wouldn’t notice that they were missing when they finished their meeting in the corner.

Four hours later, when the entire house of students was growing antsy with cabin fever and abuzz with irritated murmurings, Professor Snape strode in to declare that the faculty had successfully incapacitated the troll and transported it into Ministry care for relocation. He flicked his wand at the doors, nodding to the prefects, and informed them that they were free to roam the castle once again. The majority of the house filtered out of the room gratefully, and Harry and Theo did the same, heading straight for Gryffindor to tell Hermione and Ron what they’d been up to. Hermione and Ron both had difficulty believing Harry about his theories concerning the Headmaster, but eventually they conceded to at least consider the possibility until a better idea could be suggested.

Unfortunately, speculations on what exactly Dumbledore was guarding didn’t get very far. Harry and Hermione contributed a few good ideas that they mutually shot down soon enough, and then the conversation slowly devolved from productivity into idle chatter and joking. Harry returned at curfew to his room with no more ideas than he’d had earlier that afternoon.

He tried to ask Professor Snape for the pass to the Restricted Section again the next night, but the man was out of his office, and nobody answered no matter how hard he knocked. It was odd; Snape normally lived in his office until fairly late in the evening, and the students could always be sure to catch him there. Harry supposed he had to be doing something important. He filed the though away for future perusal.

Without his pass, he wouldn’t be allowed into the Restricted Section. At least, not if anybody saw him. But that was why he had an invisibility cloak, wasn’t it? Harry donned it after sundown and slipped into the library. An unexpected visit from Filch - for goodness’ sakes, he would have to memorize the blasted man’s schedule, and start carrying around fish to appease that monstrous cat - forced him to flee without getting a good look at much at all. Mrs. Norris followed him until he had to run down into the basement and hide in the nearest unlocked room.

He shut the door as quietly as he could behind himself, locking it tight so that the creepy cat wouldn’t find him. He knew she was communicating somehow with Filch, though he couldn’t divine exactly how. Anything she knew, Filch would know sooner or later, and he didn’t relish the thought of being caught by Argus Filch alone at night. He’d heard horror stories about the punishments Filch used to inflict before Dumbledore enforced ethical limits.

With a shudder, he turned away from the door and looked around the room. It was almost empty, a thin layer of dust on the floor that Harry had disturbed with his footprints. He made a mental note to wipe those away before he left; growing up with Sherlock left him feeling itchy about making such obvious tracks.

But what really commanded his attention was the old-fashioned freestanding mirror in the middle of the room. It had just as much dust as the floor, but its brass finish was untarnished and the glass was clear. He stepped over to it slowly. What was a mirror doing all the way down here, alone in a room? There were so many strange things about Hogwarts, and Harry knew he hadn’t even begun to see the tip of the iceberg. With the sleeve of his house jumper, he wiped the dust off of the glass so that he could better see.

What stared back at him was not what he knew should have been. It was him, of course, but he was older. His reflection stood taller, looking down on the real eleven-year-old Harry with a warm smile. The older Harry had grown into his glasses; they didn’t quite look like they were constantly about to fall off of his face. A Head Boy badge glistened on his vest. The empty room was filled with students of all houses and ages. They all seemed happy to see him, and even the students that hated him now, Pansy, Blaise, and the others that they held sway over, clapped him on the shoulder and congratulated him on the achievement. Harry swallowed, touching the tips of his fingers to the glass. The reflection of him mirrored the gesture, but his hand was too large to fit perfectly against Harry’s.

What was this? Obviously some sort of enchantment, but what for? He forced his eyes away from the reflection, instead examining the frame. Old, well-cared for, possibly of muggle origin and bespelled by wizards, but that last point would be hard to prove. There was lettering at the top, ‘Erised,’ was that the name of the - oh. Oh. Desire. Desire, mirrored backwards. The mirror showed Harry his heart’s desire.

He stared at the reflection for a moment before frowning. “Well, that’s useless.”

The scene in the mirror seemed to freeze for a moment, then disappeared like smoke in the wind, leaving only Harry glaring at it with one sleeve covered in dust. He clicked his tongue against his teeth disapprovingly, then abandoned the room and went back to the dormitory, falling asleep almost immediately, buried pleasantly behind the green velvet curtains of his four-poster.

Sleep didn’t last long.

Harry awoke to the sound of shouts and the strange feeling that something was wrong, like waking up upside down in bed and feeling that the world has suddenly turned itself around and lost you entirely. He pushed open the curtains around his bed and stumbled out, bare feet suddenly frigid against the cold stone. Shoving on his glasses, he could see the other students scrambling to the window. The window in the first year’s dormitory was the only one above ground, peeking out a few scant inches above the rasp of the grass. The view was awful, but it was still a view, unlike the other windows that opened onto lakewater cool and green as jade. The scene, usually rather pastoral, had turned nightmarish.

The sky was lit with flame and smoke. The little hut out on the grounds, close to the Forbiden Forest, was on fire. Goyle said something to Crabbe in what he must have thought was a whisper, and from it Harry gathered that it was the gameskeeper’s house, Hagrid. There were already professors rushing to the scene, casting strong water spells to spray down the house and prevent further damage. Judging by their firm attention and the lack of screams, it appeared that nobody had been gravely injured or killed in the fire, but the other students didn’t seem to have deduced as much, if their rapt expressions were anything to go by.

Harry watched for a few minutes before deciding that, since there was nothing he could do, he may as well go back to bed. But just before he turned away from the window, a dark shape shot out of the fire, winging through the drifting smoke and cutting through it. It was so black that it made the sky look pale, blotting out the stars for all that it was still small. Harry squinted and leaned into the windowsill for a moment before his eyes widened in surprise. A dragon! A real, live dragon. The beast had undoubtedly set off the fire, that much was certain.

The other children appeared to have noticed it as well, and the whispered word ‘dragon’ swiftly spread through the room. They all leaned against the windowsill, but the dragon had disappeared, and no more were flying out of the hut. After watching the fire burn, slowly smoldering down under the efforts of the professors, they one by one trickled off back to bed until it was only Harry left at the window, brain whirling.

In the Great Hall at breakfast, the news was everywhere. As soon as a few students found out what had happened, they all knew. Apparently the groundskeeper had decided that it was a good idea to try and raise a young dragon all by himself. The animal was already a month and a half old, and how the man had managed to keep it from starting a fire before this was anyone’s guess. It was a young Norwegian Ridgeback - the investigation of how it had been smuggled into the country was ongoing - and so Hagrid couldn’t keep it. Though he cried when they took it, the Ministry made sure that it went to a good conservation center in Romania where it would be cared for and monitored through its release into the wild. Harry heard from Ron that his older brother worked there and would get to take care of it himself, and as far as Harry was concerned, that was as good a deal as Hagrid was going to get, poor man.

Of course, several of the more academic classes were completely derailed by the chatter and gossip about the dragon smuggling. The story swiftly blew itself out of proportion, from one very small dragon to one very large dragon, then two, then a whole ring of dragon smuggling that Hagrid had stumbled into. There were even tales of other outlandish creatures like pegasi - largely understood to be a muggle fairy tale based on the misconstrued sightings of hippogriffs - that had been ‘rediscovered’ through the completely nonexistent dragon ring.

Professor Flitwick had quite the time stamping that rumor out and getting control of his class back. Harry noticed, though, that none of the Slytherins dared to whisper among themselves in Potions. He didn’t blame them. Snape was limping, a fact that Harry was already analyzing quietly, and the limp had done nothing for his temper.

By the end of the week, just around the time that the student body was growing tired of the dragon gossip and looking for a new story, Aethel dropped the latest copy of Harry’s subscriptions. There was The Practical Potioneer tied up with twine to Transfiguration Today. Both of them were lumped together with The Daily Prophet. Harry untied them and shook them out flat, glancing over the covers. He dropped his fork and stood up, the bench screeching angrily against the stone floor. The Slytherins all turned and stared at him. Harry shoved the paper at Theo, who frowned in confusion and opened his mouth to ask, then stopped, eyes widening in sudden comprehension. Grim-faced, Harry took it back and hurried across the room to the Gryffindor table. Without any further ado, he took the elbows of Ron and Hermione and tugged them up out of their seats.

“Are you kidnapping our brother?” asked one of the Weasley twins.

“Yep. Sorry. You can have him back when I’m done.”

“Keep him!” the other finished with a laugh, spearing a potato. Ron glared at him.

Hermione was rather affronted to have her dinner interrupted so suddenly, but she let Harry pull her out of the room. After the doors swung closed, he handed them the paper.

“That’s what they’re hiding! The Philosopher’s Stone! The rock that keeps you young and rich forever!”

Ron paled and Hermione skimmed the text in morbid fascination. Theo leaned against the wooden doors, arms crossed over his chest.

“And,” Harry continued, “Professor Snape’s trying to get at it! I don’t know why - yet - but it’s so obvious. That’s why he’s been limping, you see, the hellhound got his leg when he tried to get past it!”

“Maybe he doesn’t trust Dumbledore with it,” Theo suggested.

Harry tilted his head to show that it wasn’t a completely improbable theory. As things stood, like Theo, he trusted Professor Snape far more than the Headmaster. At least Snape, even if he held his prejudices a little close, had been honest with him, and had treated him like an adult. He didn’t doubt that Dumbledore had good intentions, but if there was one thing that he’d seen from the Scotland Yard, it was that good intentions didn’t go very far at all.

Ron mumbled something darkly; Harry knew that his alliances ran the reverse, trusting Dumbledore and not Snape. He supposed that he couldn’t blame him, but that didn’t mean he was about to agree.

“We’ve got to figure out why he wants it, and we’ve got to figure it out fast.”

“Where’s the rush?” Ron asked, brows knitting together.

Hermione sighed, tucking her hair behind her ear in a worried gesture. “Because if the Daily Prophet’s published about it, then Professor Snape probably isn’t the only one who wants to get it.”

Hogwarts was a different place when they were looking for danger around every corner. Theo, though he seemed to dislike the entire idea of putting his life in danger, held his cool and only snapped back with sarcastic barbs whenever anyone suggested that he wasn’t comfortable. Ron wasn’t any cozier about the entire thing, but he seemed to think that if a pair of Slytherins handle it, then it was his duty to be braver than them and suck it up. Hermione appeared to forget entirely that there was ever any danger involved, if only because she was concentrating so strongly on the academic side of it and not the actual physical side.

From what snooping Harry could do, he slowly gathered that there was, indeed, someone else after the stone. Moreover, they were in Hogwarts. Judging by a whispered conversation Harry eavesdropped on, Professor Snape was trying to get to the stone before the competitor could - just like Harry. Harry very nearly told him what he was doing, but something told him that, as much as the professor was growing to respect his intelligence, he wouldn’t allow a first-year to go off campaigning on this sort of adventure. Instead, he kept their work a secret.

He compiled a list of all the people in Hogwarts, a long scroll about three feet long in small writing. He didn’t leave anyone out except for Theo, Ron, and Hermione. All the students, all the professors, and everyone down to the last staff member were on the list. He crossed them off one by one. The eliminations went very quickly at first, and the students were the easiest to cross off. But soon enough it was down to the professors, and it was much harder to prove their whereabouts or even their opinions. There were certainly suspicions - Harry didn’t like something about Professor Quirrell, but he couldn’t put his finger on it - but nothing that he could prove. Yet.

But there was nothing like sudden clues to set things in motion. Harry was out in his invisibility cloak, snooping around the castle, when he spotted Hagrid hurrying through the halls with a desperate expression. He didn’t have to be a genius to know that something was up, so he tightened the cloak around his shoulders and hurried after. Hagrid soon went into Dumbledore’s office, climbing the round stairs and hovering, huge, in the cacophony of stuff that was the office. Dumbledore hurried over to see him.

“Hagrid, what is it?”

“The - oh, Headmaster, ‘s too horrible! There’s a unicorn, jus’ lyin’ dead in the Forest - somebody’s killed it!”

“You’re certain?”

“I’d heard rumors from th’ centaurs, but I’d hoped they were wrong. But there ‘e was, jus’…” Though Hagrid was facing away from Harry, there was a brief choked noise that told him that the man was very near tears at the plight of the creature.

Dumbledore laid a reassuring hand on Hagrid’s shoulder. “We will make sure that it’s taken care of, of course.”

“But who would do it?!”

Dumbledore only said grimly, “You know as well as I do who stands to gain from the blood of a unicorn.”

“Aye…”

“But we can hope, as you said, that we are wrong.”

Harry slipped out while both of them were too involved to notice the door sliding open and shut without anyone there.

Something was clearly amiss at Hogwarts. Someone had released a troll on Imbolc - and Harry had no doubts that the thing had been purposefully released, because no troll in their right minds would wander into Hogwarts without provocation - and now someone had killed a unicorn. That was obviously connected to the Philosopher’s Stone; it was surely the same man who needed to stoop to the use of unicorn blood to live who would also steal the Philosopher’s Stone to win back his full life. How did the troll fit in? A distraction, perhaps? A botched assassination attempt on the professors?

And more importantly, who was behind it?

His thoughts were so tangled up that he didn’t even bother paying attention to the other students in the Slytherin common room when he returned that night, not even the ones who cast him dirty looks from where they were lounging on the couches. He just climbed up the stairs to the dorm room, where Theo was working on his History of Magic essay alone. Casting a quick silencing charm on the door to make sure nobody overheard, he hurried over to Theo’s bed.

“Theo!”

Theo’s head snapped up, relieved of the chance to procrastinate on his homework.

“Harry!”

“I have something to tell you - “ both boys began, then stopped abruptly as they realized they were saying it in unison. They paused, then tried again, “You go first - “ only to stop again, finding themselves in chorus another time. Harry held up his hand, giving up with politeness for the moment, if only for the sake of practicality. Theo, falling silent at the signal, let him go ahead.

“There’s a unicorn dead in the Forbidden Forest. Whoever’s going after the stone is using its blood to stay enough alive until they can get their hands on it.”

Theo licked his lips, suddenly confused. “But that doesn’t make sense!”

“Why not?”

“Because what I was going to tell you - it’s Quirrell, he’s the one after it! I saw Snape about to bite his head off when I tried to go in and ask him a question.”

“No… no, that makes perfect sense,” Harry said. “That just means that Quirrell’s working for someone else. Someone that can’t afford to be seen in Hogwarts.”

“Like who…?”

Harry’s mouth twisted in consternation. He thought he knew exactly who, but it would probably sound ridiculous. And besides, he really didn’t have any proof yet. So he took a leaf from Sherlock’s book and said, “All I have are theories. You know as much as I do.” Which was true, but not comforting.

“So now what?”

“… Now I make a gamble.”

Harry knocked on Snape’s office door. The faint sounds of papers shuffling within paused, and then Snape called out, “Come in.” Harry entered obediently, shutting the door behind him. Snape was seated behind his desk in front of a stack of small bottles from the third year potions class. There was a pile of grade papers in front of him, covered in angry red ink that would surely make the poor Hufflepuff class quail. “Mr. Watson-Holmes. What seems to be the problem?”

“Problem, professor?”

Snape arched one eyebrow sardonically. “Students very rarely stop in to play a game of exploding snap,” he said drily. “What’s the problem?”

Harry knew he liked Snape for a reason. “Right,” he agreed, getting straight to the point. “We know that you’ve been trying to keep Quirrell from getting to the Philosopher’s Stone.”

Snape immediately stiffened, nostrils flaring as he sat up straighter, palms flat on the table, and stared down Harry. “Where did you hear a thing like that?”

“Nowhere. I figured it out. My father’s a detective.”

“… Is that so.” Harry nodded. Snape’s eyes narrowed, then he shot back, “’We’?”

Uhoh. That was a stupid slip. His parents would never have done that. Too late now. “Yeah.”

“Who might this ‘we’ be?”

“I think it would be fairer for everyone if I didn’t tell-“

“Didn’t tell me that you’ve been working with Nott, Granger, and Weasley? Is that it?”

“… Right. That.”

Snape leaned over his desk to further make his point. “I may not be a detective, Watson-Holmes, but I am no fool.”

“Nope, definitely not.”

Snorting in something that could have been either amusement or derision, Snape leaned back. “What exactly did you hope would happen when you told me this?”

Harry paused, licking his lips. “Well, sir… I guess I’d hoped we could help.”

The silence from the other side of the desk was deafening.

“I mean, we did already figure out what was going on. Without any tricks.” Or, at least, without many tricks. The invisibility cloak probably counted as a trick. As did using the troll as a diversion. And eavesdropping on staff conversations. … Well. Without bribes or threats, at least. And that was something, right? He was supposed to use tricks. He was a Slytherin.

“That display of logic aside, Watson-Holmes, this is really not a matter for students.” It was only slightly comforting that Snape didn’t try to deny that the stone existed, or that Quirrell was after it.

“We want to help! With all this secrecy around, don’t you need all the help you can get?”

“This is the Headmaster’s business, not yours! For that matter, why did you even come to me? You should have brought this directly to Professor Dumbledore.”

“Because,” Harry said evenly, “I trust you.”

Snape blinked, then sighed out, long and weary, rubbing the bridge of his nose. “Watson-Holmes - Harry,” he corrected himself, in a somewhat milder tone, “I can’t allow first-year students to go gallivanting off on dangerous assignments like this.”

“But we’ve already-“

“I know. But consider this your official warning. Stay out of this. I don’t intend to let any students in my house be killed for the sake of their curiosity.”

“Professor-“

“That is all.”

Harry sighed. “Yes, Professor,” he said, and let himself out of the office.

Theo, Ron, and Hermione had to watch out for the next few days. He needed a way in to get to the stone, but he couldn’t think of anything. Without Snape to let him in on the plot and put the last puzzle piece in place on how to get into the trap door, there didn’t seem to be any way forward. Harry was frustrated, and as much as John had raised him to be more patient than Sherlock, when he was so aggravated, his patience frayed. The little things got to him, and he snapped back, sarcasm and acid instead of soft flannel and honey. Theo, after having heard one too many comments about his Potions grade, finally tossed his book at Harry and stormed out of the library. Hermione and Ron’s silence only proved that they were closer to siding with Theo on that one. Harry wearily called it a night, and the Gryffindors returned to their common room gratefully.

It was his first real case, and it was gnawing at his brain slowly until it felt like an effort to even drag himself to class in the morning. He’d had puzzles to solve before, of course, like Professor Snape or some of the easier crime scenes that Sherlock had allowed him to come along to. But this was a case, a real one, big and meaningful and difficult and quite possibly life-threatening if he got it wrong. Was this how his father felt every time Lestrade called him up with a doozy of a murder? If so, he could understand why Sherlock got so moody whenever he was frustrated on the hunt. His already inestimable respect for John rose further for dealing with this on a constant basis.

A week went by, then two, torturously slow, and Harry did his homework, because John had raised him to be a productive member of society instead of slouching about, but it felt like every assignment was like yanking off his fingernails one by one, unbelievably painful and inhumane. His friends were starting to get worried. Ron had even offered to let him win at a game of wizard’s chess, which Harry had declined because there really wasn’t much fun in it when he already knew Ron would throw the match. It felt like the only thing that really made him feel better was Quidditch practices, when he could forget about life entirely and focus on nothing more than the wind like razors in his hair and the familiar humming of the broom beneath him. But he couldn’t fly forever, and coming down was always worse than when he’d gone up. When the third week went by, he seriously considered bashing his head against the wall until either an answer came to him or he blacked out.

The others tried to tell him to write his parents and tell them about the case, in the hopes that they might have some suggestions, but Sherlock would be the most helpful one for cases like this, and he didn’t have the innate grasp of the wizarding world that would be necessary. Besides, this was his first real case, and he wanted to do solve it himself. It wouldn’t count if he went running to his parents the first time he got stuck.

Hermione had tried to distract him with exams, and at least that was a bit more productive than wizard’s chess. He did manage to study, but he was the worst study partner of all, worse even than Ron, who could barely get through three paragraphs without doodling in the margins. He would snap at the others when they got something wrong and he would stare moodily at the pages, because it all just felt so useless, when there was someone trying to get to the Philosopher’s Stone, possibly for Voldemort, who would most likely kill him, and he couldn’t do anything about it.

It was, then, surely divine intervention that clues came from the most humble of origins.

Next part.