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.
(..) in King Richard's Crusade... ...with my beloved son Robin. I fear you have returned home to desperate times... ...when dark forces plot against our absent king. I am anxious for word of my son. Were you present at his capture near Jerusalem? Do you know which potentate holds him? (..)1991 Robin Hood: Prince of Thieves