La Tradition de Minuit plot
Clara Véry, a singer in the cabaret "Le Soleil Noir", receives a series of anonymous phone calls from someone who wants to meet her in a café at ten o'clock the next day. She decides to go anyway and is surprised to find that four other people have received the same invitation: Claude Thierry, a businessman; Édouard Mutter, an antique dealer; Béatrix, a bookkeeper; and Louis Fraipont, a butcher. The latter suspects Noël, the bar owner, of being the perpetrator, but when the man is found murdered in his room, his suspicions turn out to be incorrect. After an interrogation by the police, the five are allowed to go home, but they must remain reachable because it is believed that one of them is the murderer.