Isabelle is married to Paul. She has a lover, Pierre, whom she has been seeing regularly for the past two years. One day, Paul, he too, discovers the pleasures of desire mixed with deceit : he succumbs to the charms of a young woman named Marie. From then on the couple evolves in a double lie. Each spouse leads, as well as possible, a parallel life. But lovers are very demanding...
Isabelle is a psychoanalyst, a practice witch supposes a certain insight in the problems of others. Will she be able to unravel the contradictions in her own life ? Will Paul, who loves Isabelle, have the courage to resist Marie's growing love for him ? In the end, Isabelle and Paul will have to make a choice, "for better or for worse".