The sequel to "The Lawyer", while you are in the gas station in Whetstone, you meet a cultist (Epsilon Cult member) who ask you to kill Chris Fomage (the Epsilon founder) because he is pissed of that his promises were not made. Simply go to "The Farm" (the one visited in the mission "Body Harvest") and you enter a house (actually, the house I used is a robbable house in San Fierro, but because it has blue lights at night, just like "The Farm"), then you drive on Fomage's red Walton with dents to the meetup, another gas station, where you tell him you've done your deed, then it's done.