The plot could take many turns. Maybe Q is held captive by a mysterious group and undergoes intense mind control techniques.
Well, often in such fanfics, the story might involve Q being exposed to powerful subliminal messaging or drugs that affect their mind. This could lead to Q acting against their usual nature and causing chaos for the other characters.
Well, it could be that Cross is exposed to some sort of mind - controlling device or magic. Maybe an enemy uses a special spell to make Cross forget his true loyalties and start working for them. For example, the enemy could make Cross believe that his former friends are actually his foes and he has to fight against them.
One common plot could be Sonic being brainwashed by a powerful villain like Eggman. The villain might use some new high - tech device to control Sonic's mind. Then Sonic starts to do things that are against his friends and nature, like attacking Tails or helping Eggman steal the Chaos Emeralds. Another plot could involve an alien force brainwashing Sonic and using him to open a portal to their world for invasion purposes.
Well, it could be about an evil force taking over X Sans' mind. Maybe some powerful magic or a new villain in the fanfic universe. This brainwashing might lead him to do things that are against his normal nature, like fighting his friends or causing chaos in his world.
One idea could be that Bumblebee is taken by a group of Decepticons who plan to reprogram him. Another could be that he's taken by a secret human organization for study. Maybe he's taken by a powerful alien race to use his abilities for their own purposes.
In some fanfictions, Naruto is brainwashed to believe he is from another village. So he starts working for their goals. This could lead to a lot of interesting interactions as he clashes with his former comrades. The story might explore how he slowly starts to remember his true identity through small flashbacks and the bonds he has with his friends.
Orochimaru is often a common antagonist in these types of fanfictions. He has a history of experimenting on people and his knowledge of jutsu could be used to brainwash Naruto. He might want to use Naruto's power for his own evil plans.
Eggman is by far the most common antagonist in these fanfictions. He has the motive and the means to brainwash Sonic. He's always looking for ways to defeat Sonic and gain control over the Chaos Emeralds, so using brainwashing technology on Sonic fits right into his evil plans.
Another possibility is that it could be an alternate version of one of Cross's friends. This alternate version has been corrupted in some way and wants to drag Cross down with them. They use their knowledge of Cross's weaknesses and insecurities to successfully brainwash him, believing that they are doing the right thing or that they are actually helping Cross in some warped way.
One possible plot development could be that the team at Torchwood desperately tries to find a way to bring Owen back from wherever the rift has taken him. They might search through old Torchwood files and artifacts for any clues on how to reverse the rift's pull.
In such a fanfiction scenario, first of all, the Volturi would likely have their reasons for taking Renesmee, perhaps believing she is a threat to the vampire world order. Once taken, the Cullens would be desperate. Alice might use her visions to try to find Renesmee's location. Jacob could also play a crucial role as he has a special bond with Renesmee. He may attempt to lead a rescue mission or at least try to communicate with her while she is in the Volturi's custody. The story would be filled with drama, action, and the exploration of relationships between different characters in the 'Twilight' universe.