They are accused of 'plotting' the assassination of the prime minister. = They are accused of 'plotting' to assassinate the prime minister.
As the 'plot' unfolds [=as the story continues; as things happen in the novel, movie, etc.], we learn more about the hero's family.
He is a master of 'plot' [=he is very good at thinking of interesting stories], but his characters are not realistic.
(..) Give it up, Benedict. The lobby is swarming with cops. I think I can avoid them. But if not, I have a little - - explosive surprise for them. Since you are about to die, I will tell you the plot. Think of villains. Do you want Dracula? Hang on. I will fetch him. Dracula? I can get King Kong. (..)1993 Last Action Hero