One idea could be that Bellatrix captures Harry with the intention of using him as a bargaining chip against Dumbledore. She might think that Dumbledore would sacrifice a great deal to save Harry. Another plot could involve Bellatrix trying to turn Harry to the dark side while he's in her captivity, perhaps by showing him 'truths' about the wizarding world that she believes in. Or maybe she captures Harry to extract information about the Order of the Phoenix from him.
In a fanfiction scenario where Bellatrix captures Harry, it could start with a surprise attack. Bellatrix might use some dark artifacts or spells to subdue Harry. Once captured, Harry could be in a moral dilemma. Bellatrix could taunt him about his parents and try to make him doubt his loyalties. Harry, on the other hand, could try to find allies within Bellatrix's group, like some of the Death Eaters who might be having second thoughts. He could also discover some secrets about Bellatrix's past that he could use to his advantage in trying to escape.
Well, a plot could be that Bellatrix captures Harry and takes him to a hidden lair. She then tries to perform some dark magic on him to break his spirit. But Harry resists and uses his own magic in unexpected ways to try and escape. It could also be that Bellatrix captures Harry as part of a larger plan by Voldemort. She has to keep him alive until Voldemort arrives, and during that time, Harry tries to figure out what Voldemort is up to and find a way to warn his friends.
One idea could be that Harry discovers a hidden side of Bellatrix where she has a group of followers who are all intrigued by Harry's power. They form an uneasy alliance at first, but as time goes on, they start to respect and care for each other in their own strange way.
One idea could be a story where Bellatrix has a moment of doubt about Voldemort's methods. Maybe she starts to see the destruction he's causing and has to decide whether to stay loyal or turn against him. And Harry Potter could somehow be involved in this internal struggle of hers, perhaps by showing her a different path through his own actions and values.
One plot idea could be that Bellatrix has a change of heart early on. Maybe she realizes the error of Voldemort's ways and decides to protect Harry instead. She could use her knowledge of the Dark Arts to shield him from other Death Eaters. Another idea is that she has a secret past relationship that led to Harry being her son, and she has to hide this from Voldemort while trying to raise Harry in the wizarding world filled with danger. And a third idea could be that Bellatrix is forced to be Harry's mother against her will initially, but then grows to love him in a strange, complex way as she sees his potential and the good in him.
One idea could be a time - travel plot where Hermione somehow gets sent back in time and has to deal with a younger Bellatrix. Maybe she tries to change Bellatrix's path to the dark side. Another could be a magical duel between Hermione and Bellatrix where Harry is caught in the middle, forced to choose which side to help. Or a plot where Bellatrix, under some sort of spell, has to team up with Hermione and Harry to fight a greater evil.
One idea could be that Naruto is on a mission to capture Lemon, who is a powerful but misunderstood character. Maybe Lemon has some special abilities that are being misused by a villain, and Naruto has to use his ninja skills and his ability to understand others to bring Lemon to safety. Another plot could involve Naruto having to compete with other ninja from different villages who also want to capture Lemon for their own reasons.
One idea could be exploring Bellatrix's backstory before she became a Death Eater. Maybe she had a complex relationship with her family that led her down the dark path. Another could be a story where she has a change of heart, perhaps due to an unexpected encounter with a character like Harry Potter. For example, she could see some of her own past self in Harry and start to question her loyalty to Voldemort.
A really interesting plot could be Bellatrix being given a chance at redemption. In this fanfiction, she could start to question Voldemort's motives after seeing the destruction he causes. She might then try to secretly help the Order of the Phoenix. Also, a plot about her teaching a young Death Eater the ways of the Dark Arts and having second thoughts about it mid - way through could be fascinating.
One idea could be a time - travel plot where Harry somehow travels back in time and has to interact with Bellatrix in her younger days. This could lead to him trying to change her path before she becomes a Death Eater.
Some fanfics explore Bellatrix's family relationships more deeply. Like her relationship with Narcissa. There could be a plot where Bellatrix has to choose between loyalty to Voldemort and protecting her sister, which adds a lot of emotional depth.
Well, it could be that Fem Harry Potter is actually a long - lost relative of Bellatrix's family. Bellatrix initially hates her because of her association with Dumbledore and the Order. But as the story progresses, they find out some dark family secrets that connect them. They then have to decide whether to keep fighting against each other or team up against a greater evil, like a new dark wizard who is more powerful than Voldemort and is threatening the wizarding world.