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.
(..) After you give us your analysis thus far. There's this old man who loves this girl, and she's only years old... that's the plot. Because it's written from his perspective, you sort of understand and sympathize with him, which is kind of amazing because (..)2016 Captain Fantastic