A lovely summer day in Paris. Roger and Martine are on their way to work. "Work" is a euphemism because Martine is a prostitute in Pigalle. She is saving money to buy the house of her dreams in the country. Her husband Roger "works" for the same goal, but in a brothel for women. There, duchesses rub elbows with businesswomen, militant members of women's lib and other female pleasure-seekers.

Charles Van Horn, son of rich and powerful Théo Van Horn, calls upon his former teacher Paul Régis to help him solve the mystery of his recurring bouts of amnesia.

Marceau Léonetti, a competent and energetic officer stops by chance the son of an influential lawyer driving under the influence of alcohol. A few months later, the lawyer falsely accuses Léonetti as being violent and incompetent. As a result Marceau is transferred to a small police station, where he meets young and beautiful Jeanne. Soon they are faced with a tough investigation.