The "black robe" in the title of this suspense film belongs to a female lawyer, Florence Nat who has just lost a case in which she defended Simon Risler, a man wrongly accused of murder. Risler escapes before he can be put in prison, and seeks help from attorney Nat in finding the real killer, partly by going after the police inspector who framed him in the first place. A retired surgeon, in the process of setting up a drug rehab clinic gets involved in solving Risler's case, and soon the solution seems to be pointing to high-ranking figures with every desire and ample means to keep the truth well-hidden.

When her old resistance buddies come to her looking for someone to helm a financially troubled liberal newspaper, Judith (Simone Signoret) is at first reluctant, but for this old hero of the French anti-Nazi resistance, challenges are hard to ignore. She takes on the job, mortgaging her house to keep the paper solvent. When things take a turn for the worse, because of concerted opposition by conservative forces, she is forced to sell the paper, and she regards this as a personal failure.

Solange is seriously depressed, and her kindhearted husband, Raoul, makes it his mission to cure her doldrums. After many failed attempts to cheer her up, Raoul hits upon a possible solution: find his wife a lover. Unfortunately, his choice, Stéphane, proves to be just as ineffectual in restoring her flagging spirits. In the end, the gorgeous Solange finds her own, highly problematic tonic to her troubles in the form of a 13-year-old boy.

Pomme is a meek and mild French beautician whose life takes a fateful turn during a vacation to Normandy. She becomes the lover of middle-class literature-student François. The relationship sours when François takes her home to meet his parents, thanks in no small part to their differing social backgrounds.

After years of poverty, Carrier, a repairman, inherits a large sum of money upon his brother's death in an accident. Now rich, he decides it is time to make his mark and be known at any cost. Becoming more and more mentally unstable, he begins to threaten police and the government signing his tracts, "Armaguedon". A detective from Interpol heads the investigation and prepares a trap at an international conference of world leaders in Paris.