Harry stares at page 36 of Lycanthropy in Society. He has been staring at the page for about thirty minutes now, and he isn't doing all that well in trying to keep reading it. Hermione sits next to him, ostensibly reading over his shoulder and actually doodling flowers absent-mindedly on a scrap of spare parchment.

The other books had been quite good, honestly. Harry had been fascinated by all the history and culture in Dress To Impress, and Ministerial Insight had been quite interesting even though it was dry and sometimes lilted into lists of names, but this one?

“I don't think I can read this any more,” Harry says, looking at the illustration on page 37 of a werewolf's bloodied maw.

“It's just-” Hermione hesitates, not wanting to criticize the printed word in any respect, but struggling. “It just seems very harsh.”

“Yeah,” Harry agrees. He doesn't really know how to put it into words, the way the book feels so uncomfortable. It keeps calling werewolves animals, even when they're people sometimes, and it's… Well, the book started with a call to execute all the werewolves in the UK, which had been a shocking beginning. “Maybe we'll read it next year.”

“Yeah,” Hermione agrees, and she seems relieved as Harry chucks it aside, leaning back in the armchair. They're in the corner of the library, settled on one of the singular comfortable chairs in the ridiculously huge room, Harry sat on the seat and Hermione on the arm. The library spans forwards, and above them Harry can see three or four balconies for the next few library floors: they're on the ground floor, and occasionally a book will fly over their heads or past their table, but by now it's easy to ignore. “I'm bored.”

“I don't think I've ever heard you say that before,” Harry says mildly as he reaches for the werewolf book and drops it into his book bag. He's bored too, though. It's ten o'clock on a Saturday morning, and they have no classes for the rest of the day. Hermione doesn't really like to play games like chess or gobstones much, and Harry is avoiding Exploding Snap until the burn on his left pinky heals up.

“We've done all of our homework,” Hermione points out, watching as Harry stoppers his unused ink bottle and drops that into the bag as well. “It's only a week into term. There's nothing to really revise yet.”

“No,” Harry agrees, thinking. “Come on, get up.” Hermione frowns at him, but then she shrugs, pulling her bag over her shoulder, and they walk together through the corridors on the first floor. “How many classrooms do you think there are in the school?”

“I don't know,” Hermione says. “We have a Potions classroom, Transfiguration, Charms, History, Astronomy, Defence Against The Dark Arts… And then they use Divination, Care of Magical Creatures, Alchemy, Muggle Studies, Ancient Runes and Arithmancy.”

“So that's twelve classrooms currently in use, and then there's four or five in the school that are completely empty and that people can use to study,” Harry says. “But there are at least twelve on this floor, and at least twenty on the fifth. Think of all the doors we walk past every day.”

“They must be locked, though,” Hermione says as they approach an unmarked door, looking a little bit nervous as she and Harry share a look.

“They could be,” Harry agrees.

“They're probably completely empty,” Hermione says. “Why would there still be stuff still in old, unused classrooms?”

“You're probably right,” Harry agrees. “Probably completely empty.” He grins at her. After a pause, she grins back, and he reaches for the door handle. He grasps at it, turning it to the side, and the door opens easily under his hand and creaks slightly as he pushes it forwards. The candles around the room flicker into life, and Harry and Hermione stare into the room from its threshold. There are a few desks stacked to the right of the room, and around its edges are mostly empty shelves, but on some of them are stacked a few books, various bottles and knick-knacks, some bottles of ink and some quills.

“People use the empty classrooms all the time,” Harry says. “If we weren't allowed to look around, they'd be locked. If the stuff was dangerous, it wouldn't be here.” As one, they step inside. Hermione moves to the six or seven books stacked on the shelves, glancing through them, and Harry moves to sit behind the teacher's desk, pulling out the drawers. Nothing is dusty – the house elves keep the castle far too clean for that, and except for a few very high ceilings and occasional forgotten corners, dust never forms anywhere in the castle.

Harry pulls out some blank scraps of parchment, an unused padlock, a small mirror. The glass is mounted in clean, carved wood, and around its edges are motifs of tropical fish, its handle carved into the shape of a dolphin. It's nice. Harry wonders why someone would leave it behind.

“These are old textbooks,” Hermione says, fingering over the spines in front of her. “An equivalent of Muggle Studies, I think, but less, um, respectful.” Harry pulls a face, and he fingers the mirror in his hand before he puts it gently back into the drawer and pushes it shut again. The other drawers contain no similar treasures, but only more books about Muggle oddities.

“Oh, Harry,” Hermione says, having pulled out a book from the very back of a shelf. “Look at this.” He gets up, moving to kneel down beside her, and they page through a photo album – the photographs are sepia-toned and blurry, and the movements are jarred and stunted compared to those more modern magical photographs would make, but he smiles at them all the same. There are children playing, photographs of students passing around a ball in the classroom, a picture of a cat sprawled over the desk Harry had just been sat at. “That's so cute,” Hermione says. “I wish I had a cat.”

“Why don't you get one?” Harry asks as he turns the page, seeing the same cat curled in a ball in the desk chair. “You're allowed.”

“I've never had a pet before,” Hermione says, shrugging. “Maybe next year.”

They put the album back after they've finished looking through the albums, and with that, they move onto the next unused classroom, and then the next. It's interesting, looking through the things professors had left behind, and they talk casually about things as they go, about classes and history, about the teachers that must have taught at Hogwarts over the years.

It's nearing twelve when they go into a fifth classroom, and they stop short as they enter inside, peering into the room. They'd thought it was a classroom, anyway, but it isn't, and nor is it a broom cupboard: the ceiling is slightly vaulted, the room round and curtained with blue around its edges. In the middle of the room, illuminated by a beam of sunlight that can't be coming from any window, is a mirror.

It's tall, ornately carved with gold around the outside, and it stands on two clawed feet. The gold, so different and so much brighter than the modestly carved mirror Harry had held in his hands earlier, strikes him as almost gaudy for a moment, but as they step closer they can see its delicate design.

“What is this doing here?” Hermione asks, frowning up at it, and she steps behind it to look at the back.

“Erised strah ehru oyt ube cafru oyt on wohsi,” Harry says.

“Pardon?”

“That's what it says on the mirror.” Harry steps closer, looking up at the carefully carved in writing, and he looks inside it. He almost lets out a shout when he realizes he's not the only person in the mirror, and he stares at his reflection, momentarily horrified. And then he starts to recognize the faces. “Oh my God, Hermione--”

“What?” she asks, coming out from behind the mirror and looking at him concernedly. “What is it? Is it cursed?”

“I don't think so,” he says, reaching out and tracing over the face reflected nearest to him. When he turns to look, there's no one there.

“What do you see?” she asks, glancing at him. She stands to his right, and he looks at her strangely for a moment.

“Don't you see them?”

“I only see you,” Hermione admits, and Harry nods his head.

“Uh, it's my family, I think. My mum and dad are standing behind me, but it's not just them – it's aunts and uncles and stuff. I recognize a lot of them from photos I've been sent.” He doesn't recognize all of them, though. He recognizes some traits amongst the faces he hasn't seen before, but he doesn't know them like he does the ones he's received so far. The magic of the mirror seems to pull him in, and his heart aches for a few seconds as he looks over the faces, all smiling at him as they surround him and look proudly down at him, his family, a big family. The family he'd never had.

“Oh, wow, it shows your family?” Hermione asks, sounding fascinated.

“Yeah,” Harry nods his head, and he steps out of the way of the mirror to swap places with her. “You try!” Hermione steps in place, and she stares into the mirror, her deep, dark brown eyes widening slightly.

“Oh,” she says. Harry glances at her.

“What? Don't you see your family?” She mutely shakes her head, and she reaches out, touching the glass for a second just like Harry had, as if to see if it's real.

“No, I see me and you, some friends, and we're all at dinner together. There's a bookcase behind me, a big one, and my family are there, they're laughing with Percy Weasley… I'm wearing a suit, I guess I've got a really good job, and we all look happy. I,” she stops short, her hand going up to her face, and Harry glances at her.

“Hermione? Are you okay?”

“Yeah, yeah, I'm fine,” she says, closing her mouth and frowning at her reflection. “This is weird.”

“Yeah,” Harry agrees. He wants to keep looking, he really does, but he feels like they shouldn't. “We should go. It's nearly time for lunch.”

“We should,” Hermione agrees. She keeps looking up at her reflection, breathing in evenly and regularly. She starts to describe the books on the shelves behind her, what she's wearing, what Harry's wearing, explains how cutely ugly the cat on her mum's lap is. They swap places, and Harry tells her what his dad looks like, what his mum looks like, and then starts to describe the relatives he knows. They swap again, and then again, and then again. The mirror is… Hypnotising.

“Ah, children,” says a quiet, sage voice behind them, and Harry stops in mid-description of his Great Grand Uncle's knobbly knees, looking back towards the doorway. Professor Dumbledore stands, hands clasped neatly in front of him, watching the both of them with his old, blue eyes. “Your prefects have been looking for you.”

“Looking for us?” Hermione repeats. “But it's only-”

“It's six o'clock,” Harry says, staring at his watch, and Hermione looks horrified. “How can it be six o'clock?”

“But we've only been here-”

“Ms Granger,” Dumbledore says softly, and not at all unkindly, “Perhaps you had best go to the Great Hall and inform Mr Weasley and Ms Lanjwani of your respective safeties. Mr Potter will join you in a few moments.” Harry and Hermione share a look, and then she runs off with her book bag in tow. Harry hadn't noticed it, but he's suddenly really hungry.

“I'm sorry, sir,” he says, “We were just looking through the classrooms, and then we found this mirror-”

“Yes, Harry, the Mirror of Erised has enchanted many a young soul, and an old one. I shouldn't worry.” With Dumbledore standing beside him, a look in the mirror shows only their reflections, and Harry looks at the old man's wizened face and bright, purple robes in the glass.

“Erised. That's what it says on the mirror.”

“Yes,” Dumbledore agrees quietly, “And what do you think it shows you, Harry? This mirror?”

“It's enchanted,” Harry says, and Dumbledore gives a slow nod of his head. “It shows you- well, I don't know. It showed us different things, and Hermione is older in hers, but I'm the same age in mind, so it can't be the future, or the past, or a version of the present.” Dumbledore is watching him expectantly, which Harry takes as a cue to go on. “And it's not necessarily stuff we can achieve, because I saw- well. What I saw was impossible. So it's not the truth that it shows. It's just… What we want?”

“Do you believe it is truly that simple?” Harry shakes his head even before Dumbledore finishes the question.

“It's what we want more than anything, isn't it? What we want, like, before we even think of wanting anything else, what we want in our- in our souls? In our-” Harry's gaze flickers over the inscription again. “I show not your face,” he says softly. “But your heart's desire.”

“Yes, Harry,” Dumbledore says. “That's quite correct. The Mirror of Erised shows one not merely what they truly desire, but what they desire more than anything. Men have gone mad before its glass, my boy, but what it shows is merely a fiction. It is not a true reflection of the world around them.”

“I'm sorry,” Harry says again.

“You need not be sorry,” Dumbledore says. “Were the classrooms off-limits, they would be locked. Were their contents dangerous, they would be removed.” The arrogant part of Harry feels a smug thrill at hearing his own words come out of the headmaster's mouth, but Harry tries to stifle the feeling of satisfaction. “Nonetheless, this mirror will be rehomed quite soon. I should not advise you or Ms Granger to seek it out once more.”

“No, sir,” Harry says. “Do you, er, do you see anything, sir? When you look in it?”

“Oh,” Dumbledore says, shrugging his ancient shoulders, “I see myself holding a pair of socks.”

“A pair of- what?” The man is a loon. Draco, for once, was right.

“One can never have too many pairs of socks, Harry,” Dumbledore says wisely, and he pats Harry's shoulder in a vaguely grandfatherly way. “Make your way down to the Great Hall, now. You and Ms Granger haven't eaten since breakfast, and you are in need of sustenance.” Harry moves obediently out of the room, rushing down the corridor before Dumbledore can say anything else weird to him, and when he enters the Great Hall it is just behind Professor Snape, who turns to peer down at him.

“Oh,” he says, sounding mildly disappointed, “It would seem you are both present and alive.”

“I'll try my best to die next time, sir,” Harry promises, and Snape's lips twitch. Harry wonders for a moment if he'll say something like, “If only you meant it, Potter,” or “Five points to Slytherin for indulging my wishful thinking,” or “Very good, Mr Potter,” but Snape doesn't say any of those things.

“Eat,” he orders cleanly, and makes his way up to the staff table. Harry shakes his head at the professor's retreating back, but at least he doesn't want socks more than anything else in the world.

Every teacher at this school is a weirdo, he's convinced.