Author's Note: I do not and never will own HP.
Luna's autistic in this. Title is taken from "Shankill Butchers" by The Decemberists.
There were rules in this world, Luna knew. Saying hello back to the next door neighbour when you came pelting down the lane with bare feet and hair streaming behind you was one. If you did not say hello, then you were being rude, and he was liable to say something to your mother or father when he saw them next. So she said hello even though the way her mouth stretched over the syllables was awkward, and sometimes she was out of breath.
Wearing shoes in stores and Diagon Alley was another rule. There were even signs outside some shops. No Shirt, No Shoes, No Service. Sometimes Luna would repeat it to herself when she went in, staring down at the hated laces that tied her shoes to her feet. They guaranteed her Service, she reminded herself, and it made her feel better, skipping after her mum and occasionally pushing the trolley for her.
Her father taught her other rules. Rules like "nothing is what it seems" and "there are fantastical creatures everywhere if you know where to look." Those gave Luna trouble at first. You can't see a Nargle like a kitten dozing on the windowsill, or a frog hopping from lily pad to shore. Xenophilius taught her other ways to look, giving her a pair of Spectrespecs for Christmas when she was eight so that she could see Wrackspurts. She was shocked to discover that she could, and spent the next week wearing the Spectrespecs everywhere she went, until her mum put her foot down and told her that she needed to give them a break, or she'd run into the walls even more.
Her mother taught her the best rules. You can't make cookies without licking the spoon at least once. If you go barefoot in the house, then you can feel how soft the carpet is. If you sit still and let your mother comb your hair, she'll thread pretty ribbons through it that will dance on the wind when you run later. If you follow the directions, you can make the most brilliant Potions. Luna stirred cauldrons and mashed up unmentionable things with a spoon under Pandora's guidance, listening to her mother's soft voice lilting up and down. Her mother had the most beautiful voice and Luna could listen to it for hours. She would stand on her stool, both hands grasping the stirring rod, as she watched the liquid inside turn glossy purple, vivid green, bubbly grey. The smoke smelled like dreams.
Only then her mother broke a rule.
Luna didn't know which one it was. Her mum didn't need Adult Supervision like Luna did. But maybe she stirred counter-clockwise when she should have stirred clockwise, or she added three porcupine quills instead of five.
All Luna knew was her mother's eyes widening, a scream, telling her to run, and then-
Luna didn't want to think about what happened after that. Her father had run in, faster than Luna had ever seen him move, and he had scooped her up (and it was only then that she realised hot purple gloop covered her feet and that they actually hurt quite a bit) and her mother was in bits.
Her mother broke the rules and her mother was in pieces.
Xenophilius babbled inanities into her ear, about how everything would be okay, and Luna wondered in a rather distant sort of way if that was another rule, to tell the motherless little girl that things would be all right. She wondered if he knew it was a lie.
Sometimes the rules changed.