Ralf Milan (Lino Ventura) is a relentless hitman who must carry out his "contract" from a hotel room overlooking the courthouse in the city of Montpellier (France): he must kill a guy Louis Randoni (Xavier Depraz) before he makes compromising revelations during a judicial trial. But Milan's preparations are thwarted by the occupant of the room next door, François Pignon* (Jacques Brel*), a depressed shirt salesman - abandoned by his wife Louise (Caroline Cellier) who has left him for Dr. Fuchs (Jean-Pierre Darras), a renowned psychiatrist -, who tries to commit suicide by hanging himself from the bathroom pipes and causes a flood in Milan's room. In order not to attract the attention of the police, Milan persuades the hotel bellboy not to report the suicide attempt to the authorities, promising to look after the depressed man himself to avoid any recurrence. The hitman then finds himself hopelessly bogged down in the problems of his cumbersome neighbor, to the detriment of his mission. After a thousand adventures where Milan does not manage to get rid of Pignon, the two protagonists find themselves in prison, where the second continues to "annoy" the first.
* Jacques Brel is a famous Belgian actor and singer. He is the first to interpret the character of François Pignon, a favorite character of Francis Veber, who can be found in several comedy films.
* Jacques Brel is a famous Belgian actor and singer. He is the first to interpret the character of François Pignon, a favorite character of Francis Veber, who can be found in several comedy films.