The phrase "nefarious plot" refers to a secret and wicked plan or scheme that is intended to cause harm, deception, or wrongdoing to others. Full definition
The game has you eventually basically choosing whether to follow or go against the «Capital G» God, who has a rather nefarious plot of his own, despite representing «lawfulness.» (the-gamers-lounge.com)
Hanks, as symbologist Robert Langdon, wore a silly, swoopy hairdo and a perpetually glum expression as he uncovered nefarious plots by the Catholic Church. (thefilmyap.com)
Internet conspiracy theorists may have just uncovered the latest nefarious plot from the Illuminati. (relevantmagazine.com)