"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 ? Probably, because he is cynical, amoral and violent. Yet probably not, because he is gentle, touching, and lives in a strange and poetic universe. Then there's Dunand himself - is he really driven only by a quest for truth and justice ? And why does he slowly come to feel an affectionate, almost paternal feeling for Frédéric ? As dawn breaks, a long nightmare ends and Dunand discovers an unexpected, multifarious truth. Strangely, this truth binds him to Frédéric forever.