The film follows four families, with different nationalities (French, German, Russian and American) but with the same passion for music, from the 1930s to the 1960s. The various story lines cross each other time and again in different places and times, with their own theme scores that evolve as time passes. The main event in the film is the Second World War, which throws the stories of the four musical families together and mixes their fates. Although all characters are fictional, many of them are loosely based on historical musical icons (Édith Piaf, Josephine Baker, Herbert von Karajan, Glenn Miller, Rudolf Nureyev, etc.) The Boléro dance sequence at the end brings all the threads together.

Having fortuitously discovered a photograph in which Marthe embraces someone unknown, Étienne Dorsay becomes jealous and imagines various stratagems to identify the lover. In the meantime, he and his friends acquire a weekend house for a very low price.

The series follows the adventures of lighthearted Jean-Paul Moulin, a police Commissaire, and his team as they solve crimes.