In Montreal, the unemployed fashion designer Sophie Malaterre is shown a website, switch.com, where it is possible to switch houses with a stranger for vacation. Sophie seeks an apartment in Paris nearby the Eiffel Tower that belongs to Bénédicte Serteaux and they change apartments. Sophie arrives in Paris on Saturday morning. The next morning, policemen break in the apartment and arrest Sophie while she is having a bath. Detective Damien Forgeat interrogates Sophie believing that she is Bénédicte and she learns that a beheaded body was found in her room and all evidence of her life has been deleted.
Didier Travolta (Franck Dubosc) is a 40-year-old disco music fan who has no job, lives with his mother, and has a son he hasn't seen for a while. The mother of his son refuses to send him their son for the holidays unless he can offer him a real vacation, not just going to bars of the French port city of Le Havre. As the jobless Didier has no money, the only way he can see his son is by winning a dance contest organized by his friend Jackson (Gérard Depardieu), with the prize a vacation to Australia for two.
A second-class horror movie has to be shown at Cannes Film Festival, but, before each screening, the projectionist is killed by a mysterious fellow, with hammer and sickle, just as it happens in the film to be shown.
Because he only thinks about Karine, the wife of his best friend André, Pierre, a writer, can no longer write. The situation is all the more complex as Pierre lives with André's first wife, Mireille, whom he took from her five years ago. He confuses his computer and Karine, and talks to her. Karine's spirit is with him. André and Mireille go to a congress of surgeons in Florida, Pierre and Karine, alone, spend delicious moments together.
