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.
(..) Calm down and let me talk. Tell you what. l'll show part one another time. Quiet, quiet! l've seen the whole movie. l'll tell you the plot. Alfredo, what is it? l can't. The Host is on the altar. Father, l need you urgently... because l have doubts... (..)1988 Cinema Paradiso