After incurring the wrath of the American Mafia, a stand-up comic (Warren Beatty) flees Detroit for Chicago, taking the name Mickey One (from the Greek ethnic name Mikolas Ongeoffery on a Social Security card he steals off a homeless bum). He uses the card to get a job at a seedy diner hauling garbage. Eventually he returns to the stage as a stand-up comic, but is wary of becoming successful, afraid that he will attract too much attention. When he gets a booking at the upscale club Xanadu, he finds that his first rehearsal has become a special "audition" for an unseen man with a frightening, gruff voice (Aram Avakian). Paranoid that the mob has found him, Mickey runs away. He decides to find out who "owns" him and square himself with the mob. However, he doesn't know what he did to anger them or what his debt is. Searching for a mobster who will talk to him, he gets beaten up by several nightclub doormen. Mickey finally concludes that it's impossible to get away and be safe, so he pulls himself together and does his act anyway.