One possible motive could be to use Hermione as a bargaining chip. Maybe Narcissa wants to exchange her for something important to the Death Eaters, like information or the release of a captured Death Eater. In the wizarding world of 'Harry Potter', such power - play is not uncommon among the dark forces.
One possible motive could be to gain an advantage over Harry Potter. Hermione is Harry's closest friend and a very intelligent witch. By kidnapping her, Draco might think he can use her as a bargaining chip to make Harry do something or to get information from her that could be useful to the Death Eaters. Another reason could be jealousy. Draco has always been in competition with the Gryffindors, and Hermione's intelligence and skills might make him envious to the point of doing something drastic like kidnapping.
Hermione would likely be defiant at first. She is a brave and strong - willed character. So, she would probably try to resist Narcissa's attempts to intimidate her and would look for ways to escape immediately.
The masked man might kidnap Lucas for ransom. Maybe Lucas comes from a wealthy family in the fanfiction world, and the kidnapper sees an opportunity to get a large sum of money.
One possible motive could be that Lex Luthor sees Superboy as a threat. Since Superboy has super - powers, Lex might want to study him or find a way to control him. Maybe he plans to use Superboy's powers for his own evil schemes. Another reason could be jealousy. Superboy is often seen as a hero, and Lex Luthor, being a villain, can't stand someone having so much power and adoration.
Another motive could be that Uncle Phil has some sort of secret that he thinks Jamie has discovered. He might be worried that Jamie will expose this secret, so he kidnaps him to keep him quiet. This secret could be something related to the family's past, like a hidden treasure or a dark family secret that Uncle Phil wants to keep buried.
One possible plot could be that Rabastian has some dark motives related to Hermione's magic abilities. Maybe he wants to use her knowledge of spells and potions for his own evil schemes. He could hold her in a secret location, and Hermione would have to use her wits to try and escape or send out some sort of magical signal for help.
One possible plot twist could be that Hermione's magical abilities take on a new dimension under Narcissa's influence. Maybe she discovers a different kind of magic that the Malfoy family has secretly been practicing. Another could be that Hermione's relationship with the wizarding world at large changes. She might become more of an insider in the pure - blood society, which would cause a stir among her friends like Harry and Ron. Also, her academic pursuits could shift as Narcissa encourages her to study different areas of magic that are more in line with the Malfoy family's interests.
One reason could be that Narcissa misinterpreted Hermione as a threat to her family or something she holds dear. So she pushed her on the bed as a quick way to immobilize her.
One possible plot could be that the other characters, like Harry and Ron, immediately start a rescue mission. They might search for clues about where Dolohov has taken Hermione. Maybe they discover that Dolohov is working for a more powerful dark wizard who wants Hermione for her knowledge of magic. Then they have to face various traps and dark spells to reach her.
Obviously, Harry Potter could be the one to save her. He has a strong bond with Hermione and is very brave. He'd stop at nothing to rescue his friend. He might use some of his unique magical abilities, like his connection to Voldemort, to find her.