Oubliette
It's late at night and everyone is asleep in their little beds, all the Gryffindors, all the Slytherins, all the Ravenclaws, and all the Hufflepuffs. All the professors and all the house elves and all the rats and snakes and spiders in the corners and all the monsters in the forest. Everyone sleeps peacefully in the long winter night, when the moon is almost full and shines over the freshly fallen snow.
Except for you.
You're wearing the Invisibility Cloak that appeared in your trunk one morning and prowling the halls, looking here and there, making sure that everyone is asleep, that there's no one there to find you, to catch you, to report you. You've already spent most of this month in detention and if you lose any more points, your housemates have sworn very painful torture.
So you're quiet. You're very very quiet.
But there's still a noise in the hallways. Faint scratchings, fainter whimpers, the kind of sounds a rat would make in a trap, a cat would make in a box...
...A person would make in prison.
You hear them every night. You hear them every day. You sit in Potions and they're the loudest there, distracting you to the point of danger, and your Potions are always on the verge of explosion and the professor always frowns and takes off points.
You're going to find out what the noises are. You're going to stop them. You know you're young, you know there are wizards and witches you should tell, people that should take care of this instead of you, but you also know that Hogwart's: A History doesn't mention everything, and you've heard the fables of children who have done great things.
And you want to do many great things in your life.
Turn left, turn right, straight down this way, your eyes slowly adjusting to the dark, because a lamp would've given you away. You're certain everyone's asleep, but you're not stupid.
You come to the expanse of stone wall where the sounds were the loudest, deep in the furthest part of the dungeon, a place you're certain not even the house elves go to. There's a creak behind the wall and you press your ear against the moss-covered stones, trying to hear what's behind them.
Another creak, a faint moan, and the sounds of...chains? You think they're chains.
You think they're chains and you think that you've discovered the dark secret of Hogwart's, darker than anything mentioned in Hogwart's: A History, darker than anything you've even heard in rumour passed from student to student, because they're chains and that means that, behind that wall, the wall with no door, there's someone there.
You look around one more time before slipping off your cloak and pulling out your wand. A deep breath, a swish and a flick, and you're about to chant a communication charm you read in a book when, suddenly --
There's a hand on your wrist, stopping you from moving. "It's awfully late," the owner of the hand says. "Everyone else is asleep."
You lower your hand and look at the person. The river that is her long white hair cascades down her back, stray curls pointing in every direction. Her robe is half-open, revealing a plain faded blue flannel gown and matching slippers, and she looks at you with just a hint of resignation. "You should be asleep," she says softly, "and not about to cast very dangerous spells in the dungeons."
You take a step back, and nervously glance between her and the wall. "I heard things. I heard noises. All year long. And I heard chains. Tonight. I heard things," you repeat, your throat dry.
She nods. Her hand reaches towards the wall, barely an inch from touching. She stands there for a minute, her eyes closed and her hand almost touching, then lowers her hand and smiles at you. "You've done a lot of extra reading, haven't you?" she asks.
You straighten. "Yes," you say, you voice clipped. How dare she change the subject like that? There's someone behind there and she's talking about your reading?
She smiles softly. "I was much like you when I was your age...always reading, always knowing, always exploring..." She reaches up to her, pulling from underneath her gown a thin silver chain that dangles from her neck. A small medallion hangs from it, and when she holds it close to you, you see that it's a penny, cut in two, encased in crystal. You frown and look up at her, waiting her answer.
She looks down at the necklace thoughtfully. "Have you ever travelled by portkey?" she asks, distractedly.
"Once..." you reply, not understanding.
"Have you..." She pauses, deep in thought. "Have you ever wondered what would happen if you broke a portkey?"
This must be a test. "You'd be trapped wherever you ended up, wouldn't you?"
She smiles and nods. "You're very smart..." She looks up from the medallion and looks back towards the wall. "He was very smart as well...and he knew what he had to do... No way to apparate, no doors, just a single portkey that he snapped in two and sent back before breaking his wand..."
You're growing frustrated with her and her vague sentences. "Who? Who did that?"
She looks at you and shakes her head. "Not tonight," she says firmly. "It's late, and you should be in bed. If you go now, I won't be inclined to send you to detention...again." She lifts a finger and tsks at you disapprovingly. "And I don't want to see you -- or not see you, as the case is -- searching around here again...do you understand?"
You sigh and nod, looking towards the wall instead of her. "Yes, Professor Granger."
She turns back to the wall for a second, then looks at you again. "When you're older, and willing to listen," she adds pointedly, "I will tell you about this place. But until then...you're not to speak of it to anyone." Her eyes hold yours for several seconds, then her eyes crinkle in a smile. "Now, I believe, if you follow that path..." She points to a dimly light walkway to the right. "It will take you straight to the Griffyndor tower without anyone noticing you. If you hurry, you might even be able to detour in the kitchens and get hot chocolate from one of the house elves." She tilts her head and waits for you to move.
"Thank you, ma'am," you mumble before walking down the pathway. You walk a few steps, long enough to step out of the faint light and into the darkness, and you turn back to look at her.
One hand is resting on the wall and the other is wrapped around her necklace. Her eyes are closed tightly and she's muttering a charm, something you can barely make out. She chants, and there's a faint splash of light, catching two streaks of tears on her face as she looks up and notices you watching.
She shakes her head, and the door closes in front of you.