Since she separated from her husband Jean, thirty-something Isabelle has found a new lease of life. Her career, her love life, everything is going well for her. She could not be happier! But she is also a mother, a role that she takes as seriously as her work. Mindful not to upset her ten-year-old son, Achille, she pursues her love affair with Antoine in secret. When Isabelle finally takes the decision to move in with her new lover, she has to break the news to Achille. The reaction of her good-natured little boy is not what she had hoped for...