The narrative begins with Emma traveling from Paris to Berlin, seeking to overcome writer’s block by securing work at La Maison. Operating under the alias Justine, she acclimates to the brothel's rhythm, developing camaraderie with Delly and receiving mentorship from the Madam while navigating client encounters ranging from tender confessions of loneliness to awkward, mundane intimacies.
As Emma's notebook fills with observations, her emotional boundaries erode. Her secret double life strains her relationship with her sister and creates friction with her partner Stéphane. The climax arrives during an unsettling encounter when a client breaches the unspoken code of consent and safety, abruptly shattering Emma's romanticized perception of the establishment and forcing her to confront the inherent physical and psychological hazards of the profession.
In the resolution, Emma recognizes that her journey as Justine has reached its limits and bids farewell to her colleagues. She completes her manuscript, integrating both the beauty and the harsh realities of her immersion, and finally publishes the work honoring the women she lived alongside.