Well, one possible plot development could be that the Malfoys, in rescuing Harry, have a change of heart towards the whole fight against Voldemort. Maybe they start to see the error of their ways and side with Harry more openly. For example, they could use their influence in the wizarding world to help Harry gather more allies.
In this fanfic, it could be that the Malfoys rescue Harry because of Draco. Draco might have formed some sort of bond or understanding with Harry during their time at Hogwarts. So, when Harry is in danger, Draco convinces his family to save him. This could lead to a series of events where the Malfoys have to protect Harry from not only Voldemort but also from the wizarding community that might not trust their motives.
I think Dobby could also be a significant character in this fanfic. Since he has connections to both the Malfoys and Harry. He might be the one who gives the Malfoys the idea to rescue Harry or helps in the rescue in some way. Also, Voldemort or his Death Eaters could be important in the background as the threat that Harry needs to be rescued from. Their presence would constantly loom over the story, making the Malfoys' actions more dangerous and significant.
One possible plot development could be that his friends are left to pick up the pieces. They might struggle with grief and guilt, thinking they could have saved him. Another could be that Voldemort finally takes over completely without Harry to oppose him, leading to a dark reign over the wizarding world.
Well, one possible plot development could be that his friends start a rescue mission right away. They might use magic to track the vampire's lair. For example, Hermione could use her extensive knowledge of spells to create a tracking charm. Another development could be that Harry discovers some hidden power within himself while being held captive, something that he can use to either escape or fight the vampire when the time comes. Maybe he has some latent ability related to his connection with Voldemort that can be used against the vampire's dark magic.
One possible plot development could be the initial shock and confusion for both Harry and Hermione. They would have to deal with the reactions of their friends, like Ron, who might be very surprised or even a bit jealous. Then they'd need to figure out how to balance their new situation with their fight against Voldemort or other magical threats. Another aspect could be how they prepare for the baby, from finding a safe place to live to getting all the necessary baby supplies in the wizarding world.
One possible plot twist could be that Lucius Malfoy has a secret alliance with Dumbledore all along and saves Harry to fulfill some greater plan against Voldemort. Another could be that Narcissa Malfoy, out of a mother's love for all children (not just her own), decides to protect Harry. Or perhaps Draco Malfoy betrays Voldemort's orders to kill or capture Harry because he has developed an unexpected friendship with Harry during their years at Hogwarts.
One possible plot development could be that Harry discovers his magic earlier on his own due to the neglect. He might start exploring the wizarding world secretly, finding hidden magical artifacts in the neighborhood. Another could be that he forms an unexpected alliance with the local magical creatures that sense his isolation. Maybe he even starts teaching himself basic spells from an old, dusty spellbook he finds in the attic.
Well, it could start with Severus being a vampire in secret and Harry gradually finding out. Maybe Severus initially resists the urge to feed from Harry but then some situation forces him to. For example, he might be injured and need Harry's blood to heal.
One possible plot development could be Harry having to deal with the new political and social responsibilities that come with being a lord. He might have to make decisions regarding the welfare of his land and the people in it.
Well, one possible plot development could be that Harry starts to question the existing power structures in the wizarding world. Maybe he feels that the so - called good side has its own flaws and secrets. He might then begin to amass his own power, secretly at first, perhaps by seeking out dark magic spells that have been long forgotten. He could start to gather followers who are also disillusioned with the status quo.
One possible plot development could be that Snape initially struggles with his feelings towards Harry. He has his own past grudges against James Potter, but as he sees the extent of Harry's abuse, his protective instincts kick in. He might start teaching Harry advanced magic in secret, away from the prying eyes of the other Hogwarts staff and students, especially those who might be skeptical of Snape's motives.