The story centers on Séverine, a young and beautiful woman trapped in the routine of her married life with a successful doctor who, although he adores her, fails to satisfy her deepest desires. As her daily life becomes increasingly monotonous, Séverine begins to explore her sexual fantasies, which are intense and liberating but remain hidden beneath a façade of perfection.
One day, driven by an irresistible desire to experience something out of the ordinary, Séverine decides to work as a prostitute during the day, adopting the identity of "Belle de Jour." This new world allows her to immerse herself in her darkest desires and live adventures she never thought possible. As she navigates this double life, she faces a complicated web of emotions, encounters with various clients, and the ever-growing danger of being discovered.
At the same time, her personal life becomes even more complicated with the arrival of an attractive client—a daring young man who is drawn to the enigma of Séverine. The narrative plays with the boundaries of morality and desire as our protagonist grapples with her aspirations for freedom and the commitments of her married life. Throughout this exploration of sexuality and female identity, each step Séverine takes brings her closer to the truth about herself and the emotional cost of living in the shadows of her own passions.