The title of this French "reality" drama, which translates to Before the Deluge, is a play on Louis XVI's famous prognostication, "Apres moi, le deluge." Set in 1950, the film concentrates on five Parisian adolescents. Certain that the next war will herald the apocalypse, the youngster make plans to run off to a desert island and set up a new society. This, however, will require money, which is why the boys decide to pull off a "necessary" robbery. Idealism collapses in the face of cold reality, as the five youths suffer from the consequences of their actions. Avant le Deluge was one of a group of films cowritten by director Andre Cayatte and Charles Spaak which endeavored to explore the touchy social issues of the day: others in the Cayatte-Spaak canon include the euthanasia-themed Justice est Faite and the capital-punishment tract Nous sommes tous des assassins.

Paris 1838, Prince Rodolphe vows on the deathbed of his friend Matilde to find Germain, the woman's son kidnapped by his father at birth. Disguised as a tramp, he wanders the city's slums encountering various characters who either help or hinder him.

A musician named Jacques Christens, is given a proposition by an old man. For ten million Francs he is asked to impersonate a certain Paul de Baer – a man who is supposedly exiled in the Amazone. Christens is told this scheme will save Mr. Baer from ruin. An adaptation of Boileau and Narcejac's "D'entre les Morts".

François Donge, a rich industrialist and womaniser, meets a girl nicknamed Bébé who he marries. Ten years later, poisoned by his wife and dying in hospital, he recalls his married life and understands how his wife who adored him suffered from his many affairs and indifference.