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.

The movie starts with an interview with director Claude Lelouch. He pleads viewers not to disclose the plot of the movie after leaving the projection room. Even the movie's trailer shows only a long sequence of faces gazing speechlessly in space. "Like all my movies, this one is about a man and a woman", says Lelouch in the interview.

The plot is about a trial against three men who tried to earn loads of money by illegal methods to get to Canada and about the lawyers and the judge who get on with the trial and who are being unfaithful to their couples.