ALL THE COLORS OF THE DARK

Jane Harrison lives in London with her boyfriend Richard Steele, a pharmaceutical salesman often away on business trips. After losing her unborn child in a car accident, Jane has been unable to engage in sex with Richard, while still dealing with the trauma of witnessing her mother's murder at a young age. Despite Richard's skepticism of psychiatry, Jane's sister Barbara takes her to consult a psychiatrist, Dr. Burton, for whom Barbara works. Jane tells Dr. Burton that she has been having nightmares of a sinister man with piercing blue eyes murdering her mother, insisting that she has just seen the same man in the waiting room.

After encountering the blue-eyed man twice on her way back home, Jane meets Mary, a mysterious woman who recently moved into her apartment building. Jane confides her troubles to Mary, and the blue-eyed man later tries to kill Jane with an axe. Under the guise of helping Jane overcome her trauma, Mary takes her to a castle where a Satanic cult led by J. P. McBrian is performing a Black Mass. J. P. sacrifices a puppy and has Jane drink its blood, before forcing himself on her while surrounded by the other members. That night, Jane and Richard reignite their sex life. While out with Richard the next day, Jane spots the blue-eyed man and flees in a taxi.

Jane continues to attend the cult's rituals, but is horrified when the latest ritual results in Mary's sacrifice. After Jane awakens in a field, the blue-eyed man, Mark Cogan, brings her back to J. P., who explains that Mary allowed herself to be sacrificed after bringing Jane in as a novice, as it is the only way to leave the cult. Attempting to flee, Jane is attacked by two German Shepherds before Mark sedates her. Jane awakens in her own bed and rushes to Mary's apartment, now occupied by an elderly woman.

One night, while Richard and Barbara are both out of town, an increasingly disturbed Jane visits Dr. Burton's office and tells him about the recent events. Despite dismissing the events as nightmares, Dr. Burton allows Jane to spend the night at his country house with an elderly couple who work as housekeepers. The next day, when Richard returns to find that Jane is not home, he alerts Barbara by phone. Meanwhile, Jane awakens and is horrified to find that the housekeepers have been murdered. She frantically calls Dr. Burton, who is in his office with Richard and Barbara. Dr. Burton privately tells Barbara it was Jane on the phone. As Dr. Burton drives off to his country house, Richard follows him.

Mark finds Jane, revealing that her mother was a member of the cult and that she was killed after trying to escape. After Jane finds Dr. Burton murdered in his car, Mark chases her through the woods and attempts to kill her, but Richard fatally stabs him with a pitchfork, noticing a tattoo on Mark's wrist. Richard later confronts Barbara at her apartment, having noticed that she has the same tattoo as Mark's on her arm. While secretly reaching for a gun, Barbara attempts to persuade Richard to join the cult, but as she leans in for a kiss, he shoots her dead with the gun.

At the hospital, Jane has a nightmare in which she is framed by the cult for Richard's murder, with J. P. posing as a police inspector. After she awakens, the police inform Jane and Richard that the cult was a cover-up for a drug ring, and that Barbara was the mastermind behind the cult. They also reveal that the man who murdered Jane and Barbara's mother died two months earlier and left an inheritance to both sisters; Barbara was planning to kill Jane to claim the inheritance all for herself. When Jane and Richard return home, J. P. attacks Richard, blaming him for Barbara's death. Richard chases J. P. up to the rooftop, where J. P. attacks Jane. Richard throws J. P. off the rooftop, killing him.

Richard kills Mark Cogan, the blue-eyed cultist, after a confrontation in the woods. Richard then confronts Barbara, who shares the cult's tattoo, as she secretly reaches for a gun.

The climax reveals that the cult’s reach extends even into Jane’s family, with Barbara implicated by her tattoo. Trust and reality remain unstable for Jane, blurring the lines between paranoia and real threat. Martino leaves the resolution tense and ambiguous, emphasizing the cyclical, inescapable menace of the cult and psychological trauma.