The plot could involve Hermione being held captive by a dark wizard who wants to use her intelligence for evil purposes. Harry, using his invisibility cloak, infiltrates the wizard's lair. He battles the wizard and his minions using his wand and the spells he's learned. He manages to free Hermione and they escape together, with Harry using a portkey he had prepared in advance. Along the way, their friendship deepens as they rely on each other for survival.
Well, it could start with Hermione showing signs of distress. Harry notices and starts to investigate. He finds out that there's a group of Slytherins who are using dark magic to mentally abuse Hermione, making her doubt her own abilities. Harry then challenges them to a wizard's duel and wins, forcing them to stop their abuse.
One possible scenario could be that in this fanfiction, Harry discovers that Hermione is being bullied by some dark - minded students at Hogwarts. He steps in immediately, using his skills and the respect he has among his peers to put an end to it. Maybe he threatens the bullies with exposure to the professors if they don't stop.
He could use his position of authority. Snape might confront the abuser directly. Since he's a teacher, he has the power to intimidate and put a stop to any immediate harm. He could also give Hermione a safe place to stay, like his own quarters (if it's within the rules of the fanfiction world).
A common plot element is the discovery of Hermione's situation. Usually, Remus somehow becomes aware that Hermione is in danger or being abused. It could be through his own observations, or maybe Hermione reaches out to him for help.
Well, perhaps he uses his influence in the wizarding world. Maybe he has some connections or knowledge that allows him to intervene and get Hermione out of the abusive situation. For example, he could use his status among the pure - blood families to put pressure on the abusers.
In this fanfiction, it could start with Hermione going to the lake for some research purpose. But things go wrong when she accidentally disturbs an ancient magic in the lake. Harry, who has a special connection to the magic around Hogwarts, senses her distress. He races to the lake and dives in. As he swims towards Hermione, he has to battle his own fears as well as the unknown threats in the water. Once he saves her, they realize that there is more to the mystery of the lake than they initially thought, and they team up to figure it out.
Well, Draco could save Hermione from abuse in fanfiction by first recognizing the signs of her abuse. Then, he might secretly provide her with protective spells or magical items. For example, he could give her a charmed amulet that wards off dark magic and physical harm. He also might use his knowledge of the Dark Arts to counter any curses or hexes that the abusers might use against her.
One scenario could be that Draco witnesses Hermione being bullied by some Death Eater - sympathizing students. He steps in and uses his quick wit and knowledge of magic to outsmart them. Another could be in a situation where Hermione is being wrongly accused of a crime and is facing abuse in the form of unjust imprisonment. Draco, having some influence in the Ministry due to his family, intervenes and clears her name.
Well, it could be that Hermione uses her time - turning device to go back in time and warn the Potters about Voldemort's plan. Maybe she disguises herself and manages to get into their hiding place, then uses her magic skills to set up powerful protective spells around them that Voldemort can't break through.
In this fanfiction, perhaps Hermione uses her vast knowledge of magic. She might save the Weasleys from a dark wizard's attack. Maybe she discovers a powerful spell to counter a curse aimed at the Weasley family.
Well, in many such fanfictions, Harry might use his magic skills. He could cast a powerful stupefy spell on the troll to stop it in its tracks and then quickly lead Hermione to safety. Maybe he also uses his quick thinking and knowledge of the Hogwarts corridors to find a hiding place where the troll can't reach them.