The ever-reliable Claude Lelouch serves up another romance-and-adventure combination plate with Happy New Year. Simon (Lino Ventura) is doing prison time, due to a jewel-theft caper. The police still have not recovered the loot, so Simon gets an early release so that they can track him to it.
He is wise to their intentions, however, and loses his tail early on. Nonetheless, his search for his old partner Charlot (Charles Gerard) leads him to reminisce about the robbery itself, and the events that led up to it.
With the encouragement of his partner in crime, who honorably gives him his share, he looks up his old flame (Françoise Fabian) even though he knows she is now seeing someone else. The story of their current love's rekindling coincides with a retelling of how they became lovers in the first place.