Ella, a 37-year-old woman, finds herself grappling with societal and familial pressure to have children, a path she is not keen on pursuing. Her father, a descendant of Holocaust survivors, nudges her to reconsider her stance on motherhood. Meanwhile, her husband, Aiden, encourages her to consult with Dr. Webber for a breast cancer screening. During the visit, Ella, burdened with anxiety about childbirth, expresses her hope for her biological clock to start ticking. Dr. Webber, however, implies that Ella's clock may be broken and proposes an experimental treatment instead.
In an effort to explore this option, Ella opts to enroll in the study, all while claiming to focus on a work project, which she ultimately abandons via a phone call. She meets Dr. Elizabeth Simmons, who confidently assures her that an implant and hormone therapy can reset her biological clock. Following her advice, Ella begins a regimen of prescribed pills, leading to unexpected and vivid hallucinations during a Rorschach test. The images she sees—a very tall woman, a family of deceased bugs, and a grandfather clock—trigger intense discussions with Dr. Simmons, who interprets the clock as a symbol of Ella's dread regarding her legacy.
Ella's journey takes a more harrowing turn when she's subjected to a sensory deprivation chamber, where she confronts her deepest fears, imagining a future with a baby while being overwhelmed by graphic scenes of childbirth. In a moment of panic, she begs to be released, but when the chamber opens, she encounters the tall woman, causing her to fall and lose consciousness. Upon awakening, Dr. Simmons reassures her that her strong reaction is positive. Despite the bizarre hallucinations that plague her daily life, including losing her color vision and seeing ordinary individuals transformed into the tall woman, Ella continues to hide her symptoms to remain in the study.
The tensions escalate when Ella attends a gathering at her friend Shauna's home, where the sight of her pregnant friend further complicates her already tumultuous emotional state. During the party, hallucinations continue to torment her, leading to an intense incident where she nearly crushes Shauna's belly with a heavy book. Disturbed by her behavior, Shauna's wife intervenes, and the situation spirals downhill. The pressure mounts as Ella’s father sustains an injury, and in a fit of rage, she destroys the grandfather clock in their home, feeling as if she were dismantling a part of her legacy.
After a tumultuous confrontation in their relationship, Ella discovers the truth about Aiden's complicity in her participation in the study, stemming from a discussion he had with Dr. Webber. This revelation sends her into a fury, prompting her to take drastic actions against Dr. Simmons and the implant she has inserted. The situation escalates into chaos as Ella tears the implant from her body in a desperate bid for autonomy and clarity.
With the police closing in and emotionally consumed by her actions, Ella finds herself at a cliff's edge. A revealing phone call from Aiden confirms the magnitude of her choices, leaving her to confront the horror that the clock was a metaphor for her father’s mortality. In a moment of despair, she leaps off the cliff, landing at the water's edge, miraculously unharmed. As she lies there, a strange fish-like creature approaches her, symbolizing yet another twist in her journey of self-discovery and uncertainty.
