In the vibrant summer of 1984 Paris, we meet Sarah, a successful children's author, who finds herself struggling with writer's block and the new challenges of motherhood following the birth of her first child. Her husband, Mehdi, a police inspector of North African origins, is deeply concerned about her lack of maternal instinct, as Sarah often tunes out their baby's cries with earplugs while she focuses on her work. Despite their open marriage—a “don’t ask, don’t tell” policy allowing both partners to explore outside relationships—tensions rise as Mehdi attempts to manage their child's care, sometimes relying on his own parents for support.
As Sarah navigates her personal crisis, her close friend Adrien, a middle-aged gay doctor, finds an unexpected friendship with Manu, a carefree young man who has recently arrived from a provincial town in southern France. Although not sexually attracted to Adrien, Manu shares a profound emotional bond with him and becomes not only his companion but also a student of life's pleasures. Adrien, infatuated with Manu’s youth and charm, chooses to embrace his role, albeit with an undercurrent of self-sacrifice in his dedication.
Living in a rundown hotel that doubles as a hub of prostitution, Manu shares a space with his sister Julie, who is striving to establish herself as an opera singer. Despite their environment, Manu maintains a friendly relationship with Sandra, a local prostitute, while their living situation falls under Mehdi's scrutiny as he leads a vice division within the police force.
As their lives intersect, the group gathers at Sarah’s mother's summerhouse in the scenic Calanques of Marseille. An unexpected turn transpires when Mehdi rescues Manu from drowning during a swimming outing, igniting a secret, no-strings-attached romance between the two. Their affair continues as they meet at a camping site near Paris where Manu works as a cook.
The dramatic tension escalates when Manu confesses his liaison with Mehdi to Adrien, who reacts violently. Shortly after, Adrien discovers troubling spots on Manu’s skin, leading to a devastating AIDS diagnosis. Meanwhile, Sarah struggles to complete her novel, prompting Mehdi to temporarily retreat to his parents' home with their baby. As Adrien emerges as an advocate for AIDS awareness, he also chooses to care for Manu privately, while Mehdi grapples with fear and guilt, uncertain if he has contracted the virus.
Haunted by his past, Mehdi seeks out Manu, who reveals his intention to take his own life. In a desperate act, Mehdi hides Manu's gun and discards it in the Seine. Both he and Sarah ultimately learn they are not infected with the virus, leading to a reconciliation in their marriage. However, Manu's condition continues to worsen, culminating in a tragic suicide facilitated by Adrien's assistance.
In the wake of Manu's death, he leaves behind tapes chronicling his life, which inspires Sarah to finally overcome her writer's block. As she embarks on crafting a novel based on these events, Mehdi expresses concern over the implications for their private lives, but Sarah reassures him with the promise of anonymity. As the story progresses, Julie prepares to relocate to Munich, while peace is restored between Mehdi and Adrien amid the painful realities of their lives, including Sandra's own HIV positive status.
By the following summer, the dynamic between Sarah, Mehdi, Adrien, and Adrien's new companion Steve, a young American, evolves, yet they come together to celebrate their child's birthday at the summerhouse along the Riviera, surrounded by the memories of the past.
