A film director, Jean, his producer, Marc, and his assistant, Lucette, board the Trans-Europ-Express in Paris bound for Antwerp. Once in their compartment it occurs to them that the drama of life aboard the train presents possibilities for a film, and they begin to write a script about dope smuggling. Subsequently, they see actor Jean-Louis Trintignant walking through the station. As seen through the eyes of Jean, Marc, and Lucette, Trintignant becomes Elias, the chief character in the script. Elias is going to Antwerp to pick up a suitcase of cocaine for delivery to an international organization based in Paris. As Trintignant acts out their labyrinthine plot, Jean and the others frequently change their minds, re-shooting, parodying, or eliminating entire sequences. Through it all Elias is confused both by the double-dealing of his syndicate compatriots and by the incompetent plotting of his creators, and he seeks release in sadomasochistic rape fantasies with Eva, an Antwerp prostitute planted by the organization. After delivering the suitcase to Paris, Elias learns that the mission was only a trial, designed to test his efficiency and loyalty to the organization. His second assignment is genuine, however, and Elias soon realizes that he is being followed by Lorentz, a Belgian policeman. Entangled in a network of disguises and suspicions, he learns that Eva is working for the police, and he strangles her in earnest in one of their sadomasochistic rituals. Aware of Elias' perverse inclinations, the police follow him to a cabaret featuring a nude-in-chains act. But the syndicate chief, Franck, is also there, and he kills Elias before the police can get to him. Their imagined screenplay completed, Jean, Marc, and Lucette disembark at Antwerp. They read a newspaper account of a real crime that closely resembles their story, and they decide to abandon the project. Leaving the train, Jean-Louis Trintignant is met and embraced by a girl who looks very much like Eva.
