American writer and poet William Brandels (Bruce Dern) lives in a state of 'frustrated success', as he can afford a lavish Paris apartment but is denied a much-coveted writer's award. William neglects his 40-ish but extremely attractive spouse Claire (Stéphane Audran). Needy for affection and further frustrated by the amorous dalliances of her live-in niece Nathalie (Sydney Rome), Claire has been carrying on an affair with William's editor, Jacques Lavolet (Jean-Pierre Cassel). But she becomes enraged when she sees William leaving the apartment of his research assistant, Charlie Minerva (Ann-Margret). Hiring an eccentric detective (Tomas Milian) to learn more about Charlie, Claire begins to fantasize William having sex with every woman he knows, including Nathalie. Her way of cutting off the affair is to forge William's signature on a bill of sale for his beloved apartment, forcing their move to the country. Becoming bored and resentful, William heads back to Paris, to ask Charlie to run away with him to New York.
Source : tcm.com