Everyone is convinced that Jerry Fletcher (Mel Gibson) has lost his mind as he sees conspiracies all around him. In his taxicab as he works all day, he twists complicated conspiracies about everything from washing machines to murder. Then, his worst fears are confirmed when one of his theories turns out to be real. Alice Sutton (Julia Roberts) works for the government that Jerry so badly distrusts but now he needs her help as he runs for his life from the man behind the theory that has become fact. With no one else to turn to, Alice finds herself turning from doubter to believer as both of their lives are in danger. Can they prove their theory before someone else dies?