One possible plotline could be that the Lestrange brothers use their dark magic and charm to gradually draw Hermione into their world. Maybe they start by showing her some dark secrets that she becomes intrigued by against her better judgment.
A possible plotline could be that the Lestrange brothers, in an attempt to get back at Harry Potter and his friends, target Hermione. They might start by infiltrating her life subtly, perhaps by disguising themselves as someone she can trust. As they get closer to her, they begin to manipulate her thoughts and feelings. They could try to make her question her loyalty to her friends and the Order of the Phoenix. They might also introduce her to a different side of the wizarding world, one filled with more chaos and power - hungry motives. This would put Hermione in a difficult position as she tries to resist their seduction while also being intrigued by the new knowledge and experiences they offer.
There are likely some out there. However, this kind of fanfiction often takes a rather dark and morally complex turn as the Lestrange brothers are Death Eaters in the original 'Harry Potter' lore. It might be hard to find ones that are well - written and don't cross into inappropriate territory.
One possible plotline could be that the Lestrange brothers, who are initially on the side of the Dark Lord, have a change of heart due to their interactions with Hermione. Maybe they start to see the error of their ways and end up helping her in some way.
Hermione is known for her strong sense of justice and intelligence. The Lestrange brothers, coming from a dark pure - blood family, might have a more cavalier attitude towards the law and a different view on power. Hermione would clash with them when it comes to ethical use of magic. For example, she would never condone their use of dark spells for personal gain. Her studious nature would also contrast with their more impulsive and power - hungry ways.
Perhaps Snape is under a spell that makes him act this way towards Hermione. He starts to give her special attention in class, praising her more than usual and even asking her to stay after class for 'private tutoring'. Hermione, on the other hand, tries to figure out if this is really Snape or if there is some dark magic at play. She may start to investigate, which could lead to an adventure of sorts as she tries to break the spell if there is one.
In a fanfiction, Rabastan could be in a situation where he's being hunted by a vengeful wizarding family. Hermione accidentally gets involved when she's exploring an old wizarding stronghold. She uses her quick thinking and magic skills, like her time - turning spell in a creative way, to outwit the hunters and save Rabastan. Another idea is that Rabastan is trapped in a magically sealed chamber. Hermione, through her ability to solve complex magical puzzles, finds a way to break the seal and rescue him. It could also be that Rabastan has a change of heart and is trying to redeem himself, but some of his former dark associates don't want that to happen and try to kill him. Hermione steps in to protect him.
She could also be calculating. Since she's so intelligent, she might be quickly assessing her surroundings, looking for any weaknesses in their captivity of her. She might be thinking about which spells she could use effectively in the given situation, or how to use the environment to her advantage.
One possible plotline could be Hermione's struggle against the control of Lestrange. She might use her intelligence to find loopholes in the slavery situation and try to free herself and others. For example, she could secretly study magic that could nullify the slave - binding spells.
Perhaps the plot is centered around Hermione trying to reform the Lestrange brothers. She might see some good in them that others don't, and attempts to bring them over to the side of good. This could lead to all kinds of situations, like her having to protect them from the wrath of other wizards who don't trust them.
Well, it could involve the Lestrange brothers having some dark motives for kidnapping Hermione. Maybe they want to use her knowledge of magic for their own evil plans, like getting access to powerful spells she knows.
To develop Hermione's character in this fanfiction, we can explore her moral compass in greater depth. When interacting with the Lestrange brothers, she has to constantly make decisions about whether to trust them or not. This could lead to internal struggles that show different sides of her. As for the brothers, they could be developed by showing their vulnerability. Perhaps they have nightmares about their past misdeeds and Hermione helps them face these demons. This would make them more complex characters rather than just being the 'bad guys' from the original story.