Two cousins related by marriage, Marthe (Marie-Christine Barrault) and Ludovic (Victor Lanoux), meet at a family wedding for the first time. Marthe is the bride's daughter and Ludovic is the groom's nephew. After a raucous wedding reception with plenty of dancing and drinking, Marthe and Ludovic are left waiting for their respective spouses, Pascal (Guy Marchand) and Karine (Marie-France Pisier), who are off having sex. While they wait, they get to know each other: Marthe is a secretary and Ludovic is a dance instructor who changes his occupation every three years. Later they dance together, even after the lights are turned off. Eventually Pascal and Karine show up, slightly disheveled, and the couples part.