One interesting plot twist could be that Hermione's teachings accidentally lead Tom Riddle to an even darker path. Maybe she teaches him advanced magic that he then uses in unexpected and malevolent ways. For example, he could use time - turning magic she showed him to manipulate historical events to his advantage.
Perhaps a plot twist is that Hermione discovers that Tom Riddle is actually being influenced by an even darker force that she has to fight against. This could add a new layer of mystery and danger to the fanfiction. She then has to not only teach him but also protect him from this unknown entity while trying to figure out how to deal with it.
Another plot twist might be that Tom Riddle starts to develop feelings for Hermione. This would completely change the dynamic as he is supposed to be a cold - hearted villain. It could create a love - hate relationship where Hermione is conflicted between her mission to teach him and her growing awareness of his complex emotions.
One possible plot twist could be that Tom Riddle's dark tendencies start to resurface despite Hermione's positive influence. Maybe he begins to secretly manipulate those around him at Hogwarts while still maintaining a facade of being a reformed child. This could lead to a rift between Hermione and some of her friends who suspect Tom but don't understand why Hermione is so trusting.
One common plot twist is that the pregnancy might be part of a dark plan by Tom Riddle. Maybe he intended it to gain some sort of power or to manipulate Hermione in a more complex way. Another could be that Hermione discovers something unusual about the baby that links it to a greater mystery in the wizarding world.
One possible plot could be Hermione using her modern knowledge and magic skills to raise Tom in a more positive environment. Maybe she teaches him about equality and kindness from a young age, which changes his view of the wizarding world and prevents him from turning into the dark lord. For example, she could introduce him to muggle culture and values, making him more accepting of different kinds of people.
It's also about the time - travel or alternate universe concepts often used. For example, if Hermione goes back in time, she has the knowledge of the future. How will she use it to deal with Tom? Will she be able to change the course of history? All these possibilities make the fanfiction really engaging. And the power dynamic between them, with Hermione's magic being more learned but Tom's having a natural, dark power, adds another layer of complexity.
Well, there could be a plot where Hermione, through a spell gone wrong, enters a dimension where Tom Riddle won the wizarding war and rules with an iron fist. She has to pretend to be on his side to survive and in the process, she discovers some redeeming qualities in him that she didn't expect. Another idea is that Hermione is researching a new form of magic that was only experimented with by Tom Riddle. As she tries to replicate his experiments, she accidentally summons a part of his spirit and they engage in a battle of wits and magic. And yet another plot could be that Hermione is sent on a mission to stop a new dark wizard who is using Tom Riddle's old methods, and in order to understand the enemy better, she uses a time - turner to go back and study Tom Riddle directly, which leads to unexpected interactions and consequences.
Well, perhaps the plot could involve Hermione actually getting through to Tom Riddle in some way. Since she's so intelligent and empathetic, she might start to make him question his dark ways while being kidnapped. This could lead to a really interesting internal struggle within Tom. Also, there could be a twist where the kidnapping is part of a much larger plan that involves other dark wizards or witches, and Hermione has to figure out how to not only escape but also stop this bigger conspiracy. Or it could be that Hermione discovers a secret about Tom Riddle's past during her captivity that she can use to her advantage.
One plot twist could be that the time travel is not accidental. In a fanfic I read, Dumbledore sent Harry back in time on purpose to try and redeem Tom Riddle. This changes the whole perspective of the story as it shows Dumbledore's more proactive and perhaps riskier side in dealing with the threat of Voldemort.
One possible plot could be the exploration of how Hermione's strong will and intelligence clash with Tom Riddle's dark and manipulative nature within the context of a forced marriage law. Maybe she tries to reform him in some ways.
Well, one intriguing plot is when Hermione goes back in time to stop Tom Riddle from making Horcruxes. It adds a whole new layer of drama as she has to figure out how to do it without disrupting the timeline too much. Another plot is when she travels back and tries to befriend Tom as a child, thinking she can change his future that way. In some fanfictions, the plot of Hermione getting trapped in the past while dealing with Tom Riddle's rise to power is also very interesting.
She could also become more confident in her own magical abilities. Since she is in a position to teach Tom Riddle, who is known for his magical prowess, she has to be really good at what she does. This could lead to her exploring more advanced magic herself and growing as a witch.