Well, perhaps Stiles gets used as a bargaining chip against his friends. The alpha pack might want something from Scott or the others, and they think Stiles is an easy target to control them.
The alpha pack might kidnap Stiles to send a message. They could be showing their dominance over Scott and his group. Stiles may find himself in a very dangerous situation, locked up in some sort of lair. He'd likely be trying to figure out a way to escape and get word to his friends. There could also be a sub - plot where some members of the alpha pack start to have second thoughts about kidnapping Stiles, which could lead to internal conflict within the pack.
Perhaps in this fanfiction, the Alpha pack kidnaps Stiles because they see him as a key to something bigger. Stiles is a very intelligent character, and they might want to use his brainpower for their own evil plans. He could be held in some sort of dark and spooky lair. His friends would then have to figure out where he is, and in the process, they might discover new things about the Alpha pack and their motives. There could also be some internal conflict within the Alpha pack regarding what to do with Stiles.
Well, perhaps the alpha pack kidnaps Scott to use him as a bargaining chip against his friends. They might want something in return like some kind of powerful artifact or information.
Scott would be the most likely one. He's Stiles' best friend and the True Alpha. He would never let the Alpha pack harm Stiles and would go to great lengths to rescue him.
Well, aside from Stiles, Scott is bound to be a central character. Their friendship is so strong that Scott would immediately start looking for ways to rescue Stiles. Derek Hale is another likely character. Given his past with the alpha pack and his relationship with Scott and Stiles, he would have a role to play. Then there's Allison. Her family's history with the supernatural means she has skills and knowledge that could be useful in rescuing Stiles. She could be involved in the search and rescue operation, using her archery skills and knowledge of the supernatural world to help out.
In this kind of fanfiction, Stiles might decide to leave the pack due to feeling constantly underestimated or unappreciated. He could go off on his own and start to develop his own skills and relationships outside of the pack dynamic. Maybe he finds new allies who value him more than the pack did.
Well, in such a fanfiction, Stiles might show extraordinary courage. He could use his wits to outsmart the pack when they're being unfair or overly aggressive. Maybe he'll stand up against their unjust decisions regarding how to deal with threats in the town.
In some fanfictions, the pack meeting Stiles' family could lead to a lot of chaos at first. The pack has their own supernatural quirks, and Stiles' family might be shocked or confused. For example, they could mistake some of the pack's abilities for magic tricks at first. But eventually, they might come to accept the pack and see them as an extension of Stiles' life, leading to a big family - like bond.
Well, it could go in many ways. Maybe they would be really protective at first, sizing her up to make sure she's good enough for Stiles. They might test her loyalty or her ability to keep their secrets if they're a supernatural pack.
Perhaps Stiles discovers some dark secret about the alpha pack that endangers the entire town or the supernatural world he's a part of. In his sense of responsibility and his unique way of thinking, he figures that killing the alpha pack is the only solution to prevent a greater catastrophe. This can add a lot of depth to the fanfiction story, exploring Stiles' moral compass and his ability to make tough decisions.
In this fanfiction, Kate might be working for a greater evil. She kidnaps Stiles to force him to do her bidding. Maybe she needs him to break into a secure location or decrypt some important information. Since Stiles is often portrayed as clever, she might think he can solve a problem for her.