"Un Crime" takes place over a single night, between 10pm and 6am. It takes place in a single setting - a millionaire's apartment in Lyon. The film is about the conflict between two men, alone, face to face in the closed world of the apartment. The first man is a famous lawyer named Dunand. The second is Frédéric Chapelin-Tourvel, Dunand's rich client, twenty years his junior. Throughout the night, Dunand tries to track down the truth. Did Frédéric kill his father and mother, in particularly barbarous circumstances ?