One possible plotline could be that Hermione breaks her leg during a Quidditch match while she's trying to catch the Snitch. Her friends then have to take care of her and help her keep up with her studies. Another could be that she breaks it while exploring a dangerous part of the Forbidden Forest and they have to figure out how to get her safely back to the castle.
Maybe in the fanfiction, Hermione breaks her leg in a fight against some dark wizards. This leads to her having to rely on others for protection for a while. It could also show how she copes with being temporarily disabled in a magical world where she's so used to being independent and active. She might have to learn new spells to help her move around or communicate with others when she can't easily get around on her own.
Well, Ron and Harry would most likely be main characters. They're Hermione's best friends, so they'd be right there by her side when she breaks her leg. They'd probably be the ones helping her get to the hospital wing, getting her books for her when she can't walk to the library, and generally just being there for her.
One possible plotline could be that Hermione is under the influence of a dark spell or curse that makes her lose control and harm her parents. Another could be that she is forced to do it by some dark wizard who has her parents hostage and threatens her with something worse if she doesn't. Or perhaps in a very dark and alternate universe where she has turned to the dark side for some reason and sees her parents as an obstacle to her newfound power.
One possible plotline could be that her friends, like Harry and Ron, discover her situation through some clues she managed to leave behind. They then use their magic skills and knowledge of the wizarding world to infiltrate the place where she's being held. Another could be that Dumbledore, with his vast wisdom and power, somehow senses her distress and sends a team of trusted Order of the Phoenix members to save her.
One possibility could be that Percy's friends rally around him. They might take turns helping him with daily tasks like getting to class or bringing him food. His accident could also lead to some self - discovery, as he has to deal with being immobile for a while.
Well, in some 'Hermione Disappears' fanfiction, it might be that she is targeted by a group of anti - Muggleborn wizards. They manage to make her vanish using some dark magic. Her friends, Harry and Ron, then start a frantic search. They might follow a series of mysterious clues she left behind before disappearing. It could also be that a time - traveling mishap causes her to disappear from the current timeline and she is stuck in another era.
One possible plotline could be Hermione using her intelligence to outwit her targets. For example, she might study their habits and weaknesses in the same way she studies for her Hogwarts classes. Another plotline could involve her having a moral dilemma. As an assassin, she would be taking lives, but her Gryffindor values might conflict with this. She could struggle with whether to follow orders or do what she believes is right. A third plotline could be her forming an unlikely alliance with other characters. Maybe she teams up with someone from the wizarding underworld who has skills she needs to complete her missions, and together they face various challenges and enemies.
Maybe it's a post - Hogwarts story where Hermione, in a more grown - up and jaded world, takes up smoking as she faces the challenges of the wizarding world politics or her own personal demons. It could be a way for the author to show her in a more complex and less - than - perfect light, adding a new dimension to her character.
A possible plotline could be Hermione getting captured by Greyback's pack. She then has to use her wits and magic to escape. Maybe she befriends a young werewolf within the pack and uses that connection to her advantage.
One possible plotline could be Hermione getting to know Dolohov in an alternate universe where he has a different side to him. Maybe she discovers some hidden good in him and tries to redeem him.
One possible reason could be a curse gone wrong during a spell - casting experiment. Maybe she was trying a new and complex spell and something backfired, affecting her legs.