In the fan fiction, it could be that Severus rescues Harry not out of any new - found love for the boy, but because he discovers that the Dursleys are part of a plot to bring back an ancient and powerful dark force. By rescuing Harry, he hopes to stop this plot. Harry, on the other hand, is initially suspicious of Severus' motives but as they face various challenges together, they start to understand each other better.
Perhaps Severus, while rescuing Harry, stumbles upon a hidden connection between the Dursleys and the Death Eaters. This would add a whole new layer of danger and mystery. He might have to fight off some of his former allies to get Harry to safety. It could also lead to a change in Severus' perception of Harry as he realizes the boy has been in more danger all along than just from Voldemort.
Well, perhaps in the fan fiction, Severus saves Harry from the Dursleys but then has to deal with the consequences of going against Dumbledore's plan. Dumbledore might have had a reason for leaving Harry with the Dursleys, and Severus' actions could set off a chain of events that changes the whole wizarding world. Also, Severus could find out that the Dursleys were part of a much larger conspiracy against the wizarding world, and by saving Harry, he uncovers this plot.
His character could also develop in terms of loyalty. At first, he might be rescuing Harry for some self - serving reasons, like to gain favor with Dumbledore or to stop a threat to the wizarding world that he discovers is related to the Dursleys. But as he spends time with Harry, he could develop a genuine loyalty towards the boy, which is a big shift from his previous animosity.
Maybe Severus discovers some dark magic plot that involves the Dursleys harming Harry in a more serious way. So, he intervenes just in time. He could use his skills in potions and magic to subdue the Dursleys if they resist, and then take Harry to a safe place, like his own secret hideout or a friendly wizard's home.
Perhaps in this fanfic, Severus doesn't just save Harry physically from the Dursleys. He also saves Harry from the emotional and psychological damage that the Dursleys have been inflicting on him. Severus, having his own traumatic past, might be able to relate to Harry on a deeper level and starts to mentor him in ways that Dumbledore never could. This could lead to a completely different Harry, more confident and less impulsive.
Well, one possibility could be that Draco has a change of heart. Maybe he realizes the unfairness of Harry's situation at the Dursleys'. He could use his family's influence or some magic skills he has to get Harry out. For example, he might create a diversion to distract the Dursleys while he sneaks Harry away.
It could be Voldemort. He might have influenced the Dursleys in some way to harm Harry, and Severus has to save Harry from Voldemort's long - reaching plans. For example, Voldemort could have placed a curse on the Dursleys' house that would eventually harm Harry, and Severus discovers it just in time.
The plot twist could be related to Snape's true motives. He might be under an Unbreakable Vow to rescue Harry from the Dursleys. In the process, Harry realizes that Snape is not as bad as he seems. This could lead to a complete change in their relationship. Harry could start to trust Snape, and Snape, in turn, could teach Harry some unique magic that he has never learned before, which is crucial for the upcoming battle against Voldemort.
One possible plot twist could be that Voldenort adopts Harry with the intention of turning him into a dark wizard, but Harry's inherent goodness starts to change Voldenort instead. Maybe Harry shows Voldenort kindness that he has never experienced before, leading to a shift in Voldenort's character.
In this fan fiction, Snape might adopt Harry because he realizes that Harry has a lot of potential that is being stifled at the Dursleys. He could take Harry to a secret location and train him not only in magic but also in self - defense and survival skills. Snape would have to deal with his own complex feelings towards Harry, as he has both resentment and a sense of obligation. And Harry would have to adjust to living with Snape, who is not exactly the warmest person. It could be a story of growth and understanding between the two.
In the 'Charlie rescues Harry from Ron romance fan fiction', it could be that Ron's romantic advances towards Harry are making Harry feel trapped. Charlie, who has a good understanding of both of them, might use his charm and knowledge of the wizarding world to create a distraction. He could introduce Harry to some new magical creatures or ancient spells, thus rescuing Harry from the awkwardness of Ron's romance.