In this fanfiction, it could be that Hermione is part of a group that is trying to rehabilitate former Death Eaters. Rowle is one of the targets. As she gets to know him, she uncovers secrets about his family and upbringing that made him vulnerable to the dark side in the first place. This knowledge then helps her and the group to better approach the rehabilitation process for other former dark wizards as well.
Perhaps the fanfiction focuses on Hermione's research into some dark magic spells and she finds out that Rowle has some knowledge about them. So, she has to get close to him to learn more. In the process, they might develop an unlikely friendship. Rowle could start to see the value in the light side of magic through Hermione's influence.
One possible plot could be that Hermione, in her quest for knowledge about the dark arts practitioners, comes across Thorfinn Rowle. She might initially be studying him as part of her research on Death Eaters. And as she tries to understand his motives and past, she gradually gets to know him on a more personal level.
At first, Hermione could be very guarded around Rowle. But as she delves deeper into understanding him, she realizes he has some unique perspectives on magic. They could start to exchange ideas, which gradually turns into a more friendly relationship. He might even start to protect Hermione from other threats in the wizarding world, seeing her as a beacon of hope for his own redemption.
You can start by looking on major fanfiction platforms like Fanfiction.net or Archive of Our Own (AO3). On Fanfiction.net, use the search bar and type in 'Hermione gets to know Thorfinn Rowle'. AO3 also has a great search function. Just be sure to check the tags and summaries to find the ones that match what you're interested in.
Well, it could be that Hermione is under a spell when she marries Rowle. The fanfiction could then revolve around how she breaks the spell and what she does after realizing she's been forced into this marriage. She might find that Rowle has some redeeming qualities despite the situation, and they could either part ways amicably or decide to work on a real relationship.
One possible plot could be Hermione's research on werewolves leading her to interact with Fenrir Greyback. Maybe she wants to understand the werewolf curse better and tries to interview him in Azkaban. Through their conversations, she discovers the dark and twisted past that led him to become such a feared and cruel werewolf.
Maybe Rowle is under the orders of a more powerful dark wizard. In the world of Harry Potter, there are always those higher - ups in the dark side who might want Hermione for her knowledge of magic, especially things like ancient spells and magic theory. So Rowle could be tasked with kidnapping her for that purpose.
Obviously, Harry Potter could be the one to save her. He has a strong bond with Hermione and is very brave. He'd stop at nothing to rescue his friend. He might use some of his unique magical abilities, like his connection to Voldemort, to find her.
In a 'Hermione gets a haircut' fanfiction, perhaps Hermione cuts her hair as a form of rebellion. She's been feeling restricted by the expectations placed on her. So she chops off her long locks into a pixie cut. This new appearance catches Draco's attention in a different way. He starts to see her in a new light and they end up having some interesting interactions that they wouldn't have had before.
Well, it could be a story where Hermione accidentally stumbles upon Fenrir in a situation where she has no choice but to interact with him. Maybe she gets lost in the Forbidden Forest and finds Fenrir's lair. At first, she's terrified, but as time passes, she starts to see the human side of him that is often overshadowed by his werewolf nature. And through their conversations, she gets to know him on a more personal level, learning about his past and what led him to become the feared werewolf he is.
She could save him by appealing to his better nature. Hermione is known for her intelligence and ability to reason. So, she might talk to Thorfinn Rowle, convince him to turn away from whatever dark path he was on that put him in danger in the first place. By showing him an alternative way, she could in a sense'save' him from his own self - destructive actions.