No one stopped Hermione from her obsessions. This was an unspoken rule of her friendship with Harry and Ron, the closest relationship of her life. She was closer to two boys her own age than she was her parents, her female friends, her boss. They had both mocked her for her interests at some point or another – the situation with SPEW still sits unpleasantly in her mind – but they would never manipulate her into stopping or try to push her down another path. Her parents had put quite a bit of effort into positive coercion. There were endless rewards if she would only relax the obsessions. Harry and Ron weren't that sophisticated.
This is typically for the best. In the case of Bellatrix Lestrange, it may have been for the worse.
Initially, Hermione didn't find Bellatrix interesting. She was one rich bigot of many; her reputation of insanity was a shallow gloss over simple cruelty. So Lestrange laughed as she tortured – Muggle or Wizarding, she wasn't the first. Until she saw an old picture in Grimmauld Place, a silent wizarding photograph where a young Bellatrix looked coyly over her shoulder at the viewer. Hermione was alone at the time. This was another thing that was unwise; a muggleborn shouldn't be walking around Grimmauld Place alone. They would never know if they had gotten all of the traps, all of the blood magics. But Hermione had met Voldemort and fought in a war and Harry and Ron would never stop her from being brave. There was an advantage to her being alone as well – no one needed to know that seeing an unexpected photo of Bellatrix sent her into the third panic attack of her life. No one (Harry and Ron) saw the desperate and widespread cutting charms she flung at the floor, ceiling, curtains. Or the way she swayed on her feet as she cast the repair spells afterwards.
Hermione would never stop herself from doing something brave. A sensible person probably wouldn't walk over to the photograph (fortuitously unharmed!) to take a better look. Hermione was not sensible and so she discovered that the Bellatrix in the photograph was younger than she initially appeared. The black backless dress had given her the impression of a teen, but if she looked at the roundness of Bellatrix's face, she was probably only eleven or twelve, not quite at puberty. A child playacting at being mature and attractive. The potential implications of that settled in Hermione's stomach like a stone.
It wasn't Bellatrix's unfortunate maturity that left the tenterhooks of obsession in her mind, however. It was the rune embedded on Bellatrix's lower back – the rune for silence. At that moment Bella Lestrange became both a person and a puzzle in her mind.
Runes were something she didn't get to talk about. She never took her studies far enough to apprentice under a master. Runes were an attempt to approach magic mathematically instead of ritually. The idea was that various cultures used different rituals to draw out fundamental and universal components of magic. If you want to levitate something then you are creating a force, moving an object or subject with that force, and either creating a force strong enough to move the mass of whatever you are levitating or you are displacing that mass to another area, temporarily. The guiding ideal of runes was to draw out a representation of these underlying factors and to combine them to form whatever more abstract goal a spell was made to reach. Theoretically, two people educated in different magical traditions could both easily learn to understand runes. The tricky thing about them, though, is that if runes were pure physics, a sufficiently powerful wix could imbue them with power, change pure physics into engineering with nothing more than wilful magic.
Voldemort was one of those wizards. The Lestrange family had several powerful magic users. In all likelihood, the rune on Bellatrix's back was an attempt to literally silence her. To stop her from speaking, possibly from any form of vocalization. Theoretically, it could have been to stop her from screaming.
The rune for silence was beautiful. This is contradictory. It makes Hermione mad. She still wants the world to be orderly and for horrid things to be ugly. The rune is a central dot, that stands for 'sound'; a trifecta of smaller dots that represent removal; a braided thread – 'control over'; sweeping lines like desert grasses for the bodies of animals; a single eye for the human; and an angular pattern on the edges for objects. It's simple, repetitive, it would probably take five minutes for Hermione to draw it out. What would it take to get a twelve year old to stay perfectly still for that process? The thing is, whether it hurts to put activated runes on another human being depends entirely on the specifics of the process. The thing is, every wix has the ability to paralyze another. Hermione did so when she wasn't quite twelve.
This is where it should have ended. If Hermione had a sense of restraint. The wizarding world was small and Hermione was a distinguished war hero and a young voice of inspirational change. Her boss's boss was the Minister for Magic. It wasn't hard for her to ask where Bellatrix was held after the war. She slept on it, for one night and then another. This was morally wrong, what she wanted to do. She would have been disgusted by anyone else who suggested this violation. The scar on her arm ached sometimes. The skin raised and pale, drawn too tight when she moved too quickly. It only took a week to wear down her own moral quibbles. She grabbed the bottle of henna powder from the shelf in her closet and went to face one of her worst enemies with a rune of her own creation - paradise.