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.
(..) Poopy day? So... ...what do you do? - What do I do? - Mm-hm. I'm the key figure in a government plot to deny the existence of extraterrestrials. It's a global conspiracy with key players in the highest levels of power. And it reaches down into the lives of every man, woman and child on this planet. (..)1998 The X Files