Killer Nun

Sister Gertrude returns to the Catholic hospital for the elderly after surgery to remove a brain tumor. She is plagued by anxiety, convinced that her cancer has returned, despite reassurances from Dr. Poirret. The Mother Superior dismisses her symptoms as hypochondria, while Sister Mathieu privately contends that the worry is legitimate.

She starts venturing into the city to pursue sexual encounters and begins intravenously abusing morphine and heroin that Sister Mathieu steals from the hospital. Dr. Poirret notes a troubling change in her personality as she mistreats patients. She also revels in reading gory hagiographies about tortured saints, signaling a disturbing new fixation.

Exploiting her transformation, Gertrude engineers the dismissal of Dr. Poirret from the hospital. The scandal and her increasingly erratic behavior create an atmosphere of fear and shifting loyalties. A replacement is eventually hired to fill Poirret's position.

While Gertrude is in a drug-induced state, Sister Mathieu's grandfather, a hospital patient, is bludgeoned to death with a lamp and defenestrated to look like suicide. Sister Mathieu discovers Gertrude's veil on the body and pledges to protect her, promising to burn the evidence to hide it.

Dr. Patrick Rowland is hired as Poirret's replacement, signaling a shift in hospital leadership. Gertrude's manipulation continues to shape the institutional response as new staff settle in. The atmosphere grows tenser as more deaths occur.

During a rainstorm, Gertrude witnesses Jonathan, an elderly patient, having sex with a young orderly outside the hospital. She later awakes from a nightmare in which she suffocates Jonathan, unsure if the dream is real. The next morning, Jonathan's corpse is found lying in the grass.

The events surrounding Jonathan push Gertrude into a nervous breakdown as she struggles to distinguish reality from dangerous fantasies. Her grip on sanity continues to slip as more violence unfolds within the hospital. She becomes increasingly isolated from others.

Janet, another patient, is bound and gagged by an unseen assailant and ritually stabbed in the face with needles, her head and neck slashed by a scalpel. The brutal crime shocks the hospital community and deepens the sense that a killer is at work. Gertrude remains uncertain about her own role in the violence.

Janet's lifeless body is found hanging in an elevator shaft, prompting panic and a controlled response from the staff. Dr. Poirret sedates a panicked Gertrude to prevent further breakdown. The investigation into the murders intensifies as the hospital tries to maintain order.

Gertrude confronts Peter, a middle-aged patient on crutches, who claims to know who is committing the killings. She believes she is being framed, but Peter refuses to reveal more. Later, Peter's body is found in the boiler room and Gertrude steals his crutches in a moment of frantic desperation.

The Mother Superior scolds Gertrude for her behavior and has her escorted to an isolation cell where she will be sedated. The hospital's mechanism of control tightens as Gertrude is cut off from others. Her withdrawal deepens as she remains separated from the world outside.

Sister Mathieu confesses to Dr. Roland that she has been stealing drugs to aid Gertrude and threatens suicide if she is exposed. She then begins to seduce him, complicating the hospital's already tangled web of loyalties. The confession ties her to the unfolding violence.

While detoxing in her isolation cell, Gertrude recalls the hospital's first murder—the grandfather of Sister Mathieu—and realizes Mathieu was the perpetrator. She understands that her own violent perceptions were fueled by drug haze, not actual guilt. The revelation leaves her psychologically fragile, still dependent on drugs and haunted by the truth.