Dementia 13

During a late-night row on the lake, John and Louise argue over the terms of his mother's will. John suffers a heart attack and dies, informing Louise that she will receive nothing if he dies before his mother. Louise sinks his body to the lake bottom and hatches a plan to pretend he is still alive so she can access the inheritance.

With John gone, Louise seeks to ingratiate herself with the Haloran family and secure a place in the will. She types a letter to Lady Haloran inviting herself to the family’s castle in Ireland while her husband is away on business. The goal is to manipulate the will and position herself for a share of the fortune.

Louise arrives at the castle, entering a world of old money and superstition. John's brothers Billy and Richard take part in a bizarre yearly ceremony with their mother for Kathleen, the deceased younger sister. The rite underscores the family’s fixation on Kathleen and the weight of their grief.

During the ceremony, Lady Haloran faints as she does every year, apparently over Kathleen’s memory. She explains the fainting if a fresh flower dies near Kathleen's grave, revealing her emotional fragility and superstition. Louise observes the ritual and its emotional grip on the family.

To simulate Kathleen’s communication from beyond the grave, Louise steals Kathleen’s old toys and places them at the bottom of the estate pond. She calculates that the items will surface in daylight as a ghostly sign to convince the old woman. The scheme aims to manipulate Lady Haloran and the family further.

Louise dives into the pond, believing she has glimpsed Kathleen’s perfectly preserved corpse at the bottom. She surfaces in horror, and an unknown assailant attacks her with an axe, dragging Louise’s corpse away and deepening the mystery. The incident marks a dangerous turning point for everyone at the estate.

Concerned family doctor Justin Caleb arrives and begins questioning the family, probing motives and alibis. He pieces together inconsistencies and suspicious behavior as he works to solve the entangled family tragedy. His presence introduces a rational counterpoint to the supernatural fears gripping the estate.

The killer decapitates a man named Simon, who has been poaching on the estate. The brutal act signals that someone is willing to go to extreme lengths to protect Kathleen’s memory and the family secret. The murder escalates the sense of peril surrounding the Halorans.

Dr. Caleb drains the pond, revealing a shrine with a headstone reading 'Forgive Me, Kathleen.' The discovery ties the watery site to Kathleen’s death and the family’s ghostly fixation, deepening the mystery. The shrine confirms that a hidden truth lies beneath the surface.

The following night, a shadowy figure attacks Lady Haloran, but she escapes and collapses in the castle courtyard. The assault underscores that the killer is among the household and willing to strike at the matriarch. Fear tightens its grip on the estate.

Dr. Caleb uses an obscure nursery rhyme, recited by Billy under hypnosis, to unlock a memory that leads to Louise’s frozen corpse hidden in a meat locker. Next to the body is a wax figure of Kathleen, a haunting reminder of the deception. The discovery shifts the investigation from superstition to a human crime.

To lure out the killer, Dr. Caleb places the wax Kathleen figure in a public square, turning the estate tragedy into a visible, communal trap. The plan hinges on provoking a reaction from the culprit. Tension mounts as onlookers become unwitting witnesses to the unfolding scheme.

Guilt-stricken over Kathleen’s death years earlier, Billy becomes gibbering and prowls with violent intent, attempting to kill Richard’s fiancée Kane with an axe. The moment shows the depth of his paranoia and the danger posed to innocent bystanders. The threat intensifies as the plot edges toward a confrontation.

Dr. Caleb intervenes and shoots Billy to death with a pistol hidden in his pocket, saving Kane and ending the immediate danger. The killer’s identity remains unresolved, but the peril to the living is halted for the moment. The film closes on a grave note about guilt, memory, and inheritance.