Married couple Willy and Therese go separate ways. Willy leaves town and returns years later as a famous singer. But Therese is about to marry her best friend Peter. Little does Willy know that he and Therese now have a teenage daughter.

As young French couple Gilles and Marion officially separate, we see, in reverse order, the milestone moments in their relationship: Gilles revealing his unfaithfulness at a tense dinner party; Marion giving birth to their premature son while Gilles is elsewhere; Gilles and Marion's joyous wedding; and, finally, the fateful moment when they meet as acquaintances at an Italian beach resort, and their love affair begins.