Sarah Morton, a seasoned mystery author played by Charlotte Rampling, finds herself grappling with a severe case of writer's block, hindering her ability to produce the much-anticipated next installment of her popular detective series. In an effort to relieve her frustrations and rediscover her creativity, Sarah's publisher, John Bosload, generously offers her the use of his serene country house nestled near Lacoste, France.
Once settled into the calming surroundings, her tranquility is soon shattered by the arrival of a vibrant young woman named Julie, portrayed by Ludivine Sagnier, who claims to be Bosload's daughter. She asserts that she is on a break from work and shares intriguing tales, including one about her mother supposedly being Bosload's mistress, which seemingly complicates matters further. Julie's lifestyle is particularly boisterous, involving a series of short-lived romantic exploits with various ill-mannered men, all of which slowly ignite a competitive rivalry between the two women.
Initially, Sarah views Julie as a mere distraction—a source of intermittent amusement that disrupts her writing efforts. To shield herself from Julie’s late-night escapades, Sarah resorts to using earplugs; however, she can’t help but snoop from the sidelines, entranced by the chaos unfolding just beyond her doors. This voyeurism gradually shifts into an unsettling envy of Julie’s carefree life. Tensions rise when a local waiter, Franck, becomes entangled in their dynamic; while Julie desires his attention, he appears to be more drawn to Sarah, igniting a complex triangle filled with both desire and resentment.
The atmosphere takes a darker turn following a careless night of flirting and intrigue, culminating in Franck's unexpected disappearance after a disturbing encounter at the pool. Sarah, peering from her balcony, witnesses a troubling interaction before Franck flees. The next day, Franck is nowhere to be found. In her quest to unravel the mystery of his absence, Sarah uncovers shocking truths about Julie's background, including that her mother has been deceased for quite some time—a detail that Julie deceptively concealed.
As Sarah returns to confront Julie, the tension escalates when the distraught young woman confuses Sarah for her mother and spirals into a mental breakdown. After a harrowing confession, it is revealed that Julie's rejection led to a fatal act of violence against Franck, and his body now lies hidden in a shed, buried beneath freshly disturbed soil. To cover up the grim discovery, Sarah uses her charm to distract the elderly gardener, Marcel, while silently conflicted by the chaos surrounding her.
In the aftermath, Julie expresses her gratitude to Sarah and leaves behind a poignant gift—a manuscript of an unpublished novel authored by her deceased mother, which she previously accused John of destroying. With renewed inspiration and a heavy heart, Sarah returns to England, ready to present her newly crafted story to her publisher. Just as she departs his office, she encounters another young woman—one who is an entirely different daughter than the tumultuous one she spent the weekend with.
