A man (Davos Hanich) is a prisoner in the aftermath of World War III in post-apocalyptic Paris where survivors live underground in the Palais de Chaillot galleries. Scientists research time travel, hoping to send test subjects to different time periods "to call past and future to the rescue of the present". They have difficulty finding subjects who can mentally withstand the shock of time travel. The scientists eventually settle upon the prisoner; his key to the past is a vague but obsessive memory from his pre-war childhood of a woman (Hélène Chatelain) he had seen on the observation platform ("the jetty") at Orly Airport shortly before witnessing a startling incident there. He had not understood exactly what happened but knew he had seen a man die.
Hitman Jef Costello (Delon) lives in a single-room Parisian apartment whose spartan furnishings include a little bird in a cage. A long opening shot shows him lying on his bed, smoking, when the following text appears on-screen:
Regina "Reggie" Lampert (Audrey Hepburn), on a skiing holiday in Megève, tells her friend Sylvie Gaudel (Dominique Minot) that she has decided to divorce her husband Charles. She then meets a charming stranger, Peter Joshua (Cary Grant). When she returns to Paris, her apartment is completely empty, and police inspector Edouard Grandpierre (Jacques Marin) notifies her that Charles has been murdered while leaving Paris. Reggie is given her husband's travel bag, containing a letter addressed to her, a ticket to Venezuela, passports in multiple names, and other items. At the funeral, three odd characters show up to view the body. One sticks the corpse with a pin and another places a mirror in front of the body's mouth and nose, both to verify that Charles is really dead.
The film stars Jean-Pierre Léaud as Paul, a romantic young idealist and literary lion-wannabe who chases budding pop star, Madeleine (Chantal Goya, a real life Yé-yé girl). Despite markedly different musical tastes and political leanings, the two soon become romantically involved and begin a ménage à quatre with Madeleine's two roommates, Catherine (Catherine-Isabelle Duport) and Elisabeth (Marlène Jobert). The camera probes the young actors in a series of vérité-style interviews about love, love-making, and politics.
Tom Ripley (Dennis Hopper) is a wealthy American living in Hamburg, Germany. He is involved in an artwork forgery scheme, in which he appears at auctions to bid on forged paintings produced by an accomplice, artificially driving up the price. At one of these auctions, he is introduced to Jonathan Zimmermann (Bruno Ganz), a picture framer who is dying of a rare and unspecified blood disease. Zimmerman refuses to shake Ripley's hand when introduced, coldly saying, "I've heard of you" before walking away.
French secret agent Josselin Beaumont is sent to kill Colonel Njala, the dictator of Malagawi, a fictional African country. However, before he manages to accomplish his mission, the political situation changes drastically and the French secret service resorts to handing over Beaumont to the Malagawian authorities. After a long, unfair trial, during which Beaumont is injected with drugs, he is sentenced to long-term penal servitude at a "re-education camp".
The film begins with Alphonse Tram (Gérard Depardieu), a less than gregarious character, idly chatting to an accountant who is travelling home very late. The accountant, a man of orthodox social outlook and standing is disturbed by and fearful of this rambling loner, more so when Tram attempts to give him his bloodstained knife (in order to reduce the chances of him "doing something silly..."). They argue and the accountant puts the knife on a seat a few feet away behind them. They argue some more and then notice the knife has disappeared.
In the winter of 1945, immediately after the liberation, Jean Diego (Montand), a member of the French underground during World War II, meets Raymond, one of his comrades in arms who was believed to have succumbed in battle. On the night of that meeting, Jean encounters a homeless man named "Destiny", whose predictions about him finding the woman of his life will not be too far from reality. Jean soon starts a liaison with Malou (Nathalie Nattier), a young woman who is married to a rich man. The next hours of his and Malou's lives are underscored by extreme, dramatic events; however, as the clochard (homeless person) predicted, they find their way out of the struggle and are able to move on, leaving behind wartime and its dangers.
Policeman Jean Letellier is under pressure because the infamous gangster Marcucci escaped him publicly. Moreover during the pursuit an innocent bystander was killed by a stray bullet. Letellier is investigated for having fired the deadly bullet.
Provincial 10-year-old Zazie stays in Paris with her Uncle Gabriel (a female impersonator) for two days, while her mother spends some time with her lover. Zazie manages to evade her uncle's custody, however, and, métro strike notwithstanding, sets out to explore the city on her own.
Neïla Salah, originaire de Créteil, a toujours voulu devenir avocate. Dès ses premiers jours à l'université Panthéon-Assas, elle est confrontée au professeur Pierre Mazard, connu pour ses provocations et ses méthodes particulières. Il a un accrochage avec une étudiante arrivée en retard, qui fait une entrée assez bruyante . Il demande à cette étudiante perturbatrice de lui donner son nom, puis de définir Prénom et Nom, puisqu'il n'est pas sensé , comme de juste de connaître tous les prénoms étrangers. Il fait aussi remarquer que le droit français a évolué depuis Napoléon I, contrairement à la Charia, ce qui est vrai. Il donne pour exemple le choix des prénoms, il plaisante : " avant il fallait choisir le prénom dans le calendrier, à présent on peut appeler son enfant Carte Orange". Du coup, assez bizarrement, il est accusé de racisme. Pour se racheter et un peu manipulé par le directeur de l'université qui « ne peut plus le couvrir », Pierre est contraint de préparer Neïla à un prestigieux concours d’éloquence. Malgré son cynisme et son exigence, Neïla semble trouver en Pierre le mentor dont elle avait besoin. Tous deux vont cependant devoir tout d'abord passer au-dessus de leurs préjugés respectifs.
Dans un futur proche, un jeu télévisé intitulé Le Prix du danger fait fureur. Les règles sont simples : un homme doit parvenir à rejoindre un endroit secret, en échappant à cinq traqueurs chargés de le tuer. Si le candidat gagne, il se voit attribuer la somme de 1 million de dollars, ce qui n'est encore jamais arrivé... Le tout se déroule en pleine ville, filmé et retransmis en direct sur la chaîne de télévision CTV. François Jacquemard, un jeune chômeur, veut sortir de son quotidien morose et malgré les réticences de sa compagne, décide de participer au jeu.
Having stolen some compromising documents from a powerful and successful entrepreneur/gangster at a party, a man known as Fred (Lambert) escapes from the police and takes refuge in the underground world of the Paris Métro stations and tunnels. There he joins the dwellers and befriends several colourful characters, including others who are living under the subway to avoid police arrest. While the gangster's henchmen try to find Fred, he develops a romance with the gangster's young trophy wife Héléna (Adjani). She had originally invited Fred to the party featured at the opening of the film, and is bored with her gilded-caged life.
Louis Bourdin, un humble poinçonneur de métro à la RATP, vantard mais peureux, travaille à la station Quai de la Rapée. Il est tellement fanatique de romans policiers qu'il en écrit un lui-même. Il prend le pseudonyme de Lenormand, et intitule son roman « Rapt à la RATP » : l'histoire imaginaire du hold-up de la rame des finances, qui collecte quotidiennement la recette des stations à la fin de service, vol qu'il décrit avec un luxe de détails. Il le propose à plusieurs éditeurs. Ceux-ci le dédaignant, il en fera bénéficier, bien imprudemment, une tout autre profession ... reconnaissante, mais dangereuse !
Le film retrace le parcours des jeunes de différents milieux sociaux, ravagés par l'envie de se révolter, de tout faire exploser. Le film débute par un étrange ballet montrant les acteurs dans diverses lignes du métro parisien tentant de brouiller les pistes. Puis ils passent à l'acte en faisant exploser une aile du ministère de l'intérieur, les locaux d'une banque à La Défense, et plusieurs voitures autour du palais de la Bourse. Ils abattent le président de HSBC Europe et incendient la statue de Jeanne d'Arc à la place des Pyramides.