Eight-year-old Nelly is grappling with the loss of her maternal grandmother, who succumbed to a hereditary disease in her early sixties while living in a care home. As Nelly bids farewell to the other residents, her mother Marion and her father Stéphane clear out her grandmother's room. Nelly feels a sense of unease, believing she did not properly say goodbye to her beloved grandmother. They then journey to her mother's childhood residence to clear it as well. Upon arriving late, Nelly is tucked into her old bed by Marion.
The next morning, Marion is engulfed in grief, creating a palpable tension with her husband, which is heightened by their long-standing familiarity since childhood. During the following night, Nelly awakens to find her mother sleeping alone on the sofa, deeply stricken by the loss. In her sorrow, Marion leaves quietly in the early hours, without giving Nelly the closure of a farewell.
Seeking solace, Nelly ventures into the woods to play, where she encounters a girl her age, also named Marion, who is crafting a cabin from fallen branches. The new Marion is hospitable and invites Nelly to join her. As rain begins to fall, she takes Nelly home, where they remove their wet clothing to dry out and towel off their hair. When Nelly shares that she is visiting following her grandmother's death, Marion reveals that her own grandmother, also named Nelly, has recently passed away. As Nelly explores the house and sees Marion’s disabled mother in bed, it dawns on her that they are in her grandmother's house, and she is indeed in the presence of her mother. Alarmed, Nelly hastily departs, feeling relieved upon returning home to find her father.
Nelly finds herself in the woods once again, this time observing her mother as a young girl. They continue to construct the cabin together, and Nelly discovers that they share the same age, while also learning that Marion is due for an operation in three days—a procedure meant to spare her from developing the same debilitating illness that afflicts her mother. Through her repeated journeys back to the late 1990s, Nelly uncovers secret dreams and ambitions her mother holds, including her aspirations of becoming an actress, as they indulge in playful improvisation.
On the eve of Marion's operation, Nelly reveals her true identity to her mother, claiming to be her daughter from the future. To substantiate her assertion, she leads Marion to the now vacant house of her grandmother, where she confides that Marion's mother will die when she is thirty-one and how deeply she was loved by her. Their poignant conversation is cut short when Nelly’s father returns early, eager to ensure they are home in time for Marion's birthday. Nelly persuades her father to allow her an extra night with Marion, so they can bond further.
As the three generations come together to celebrate Marion's ninth birthday during a sleepover, the joy is palpable. After a morning paddle at a nearby reservoir, Marion prepares to leave for the hospital, and Nelly reassures her that the surgery will go smoothly. Nelly expresses her concerns about her mother's sadness, wondering if she is the cause. Marion comforts her, affirming that she believes that is not the case. They share a heartfelt hug before Marion departs.
Having returned to her grandmother’s house, Nelly is taken aback to find Marion sitting cross-legged, having returned for a final visit. In a moment of unspoken acknowledgment of their intertwining destinies, they embrace, sharing a meaningfully emotional connection as they speak each other’s names. This poignant moment encapsulates the enduring bond of love across generations.
