KNIFE OF ICE

A famous singer, Jenny Ascot, visits her artist cousin Martha Caldwell at her home in the town of Martinet, located in the Spanish Pyrenees. Martha has long been rendered mute after witnessing both her parents being killed in a train crash when she was a child, her father saving her life by throwing out of a window before the train's worst wreckage. She communicates by hand gestures and tapping on the telephone receiver. Martha deliberately meets Jenny at the station to confront her fears. They see a violent bullfighting event together, but Martha is too distressed to watch and leaves. While Jenny and Martha are travelling to Martha's home, they notice a strange man with pearly eyes who seems to be following them.

That night, following a dinner party at Martha's villa, Jenny hears noises in the house and finds a broken vase. When she investigates, she is stabbed to death by an unseen figure. The following morning, Martha finds Jenny's corpse under the car in the garage. The police believe the killing is connected to the death of a teenage girl found in a ditch before, assuming a homicidal sex maniac is at large. Martha sees the strange man stalking her at the cemetery during Jenny's funeral, and when fleeing, he drops his pendant of a goat, revealing him as a Satanist. His hideout is soon found to be an abandoned building littered with morphine, but he's nowhere to be found. Martha continuously flashes back to pieces of imagery in her mind which come from her trauma and seem to relate to the murders. She later sees a cat with their throat slashed and lying in their own blood, the same cat Christina, the adolescent daughter of a family friend, was given as a present. Martha finds some comfort and companionship in her, even accepting a Snoopy necklace from her and giving her in return a Donald Duck wind-up toy.

One morning, Martha's housekeeper Annie Britton goes to run errands in town, taking her bicycle. En route back to Martha's house along a wooded road, Annie finds a strange occult symbol rendered in red paint on a tree, the same symbol police found in the ruined building where they suspect the Satanist performed Black Masses. Annie never returns from her errand, and Martha alerts her Uncle Ralph. Late that night, Martha's friend and therapist, Dr. Laurent, visits the villa, and finds Martha in a worried state. Martha notices a spot of blood on his pants, which Dr. Laurent attributes to a patient he treated earlier. Moments later, police phone the house, and Dr. Laurent answers: They inform him that Annie's corpse has been discovered in the woods, her throat slashed. A search reveals nothing, except the goat symbol painted into the tree.

During a rainstorm, police catch the man, British hippie Woody Mason, breaking into a local doctor's office and stealing morphine, but are unable to stop him when he flees. Meanwhile, Martha cares for her Uncle Ralph, who is weakened by a heart ailment. Martha is assaulted in the home by an unseen figure when the power goes out, found with an electrical cord tied around her neck. But when police arrive to perform a wellness check shortly after, they find no one present. Police subsequently find Woody in a nearby cemetery and apprehend him, but he denies any involvement in Annie's murder, nor that of the teenage girl, whom he was dating. When questioned herself, Martha admits that she cannot positively identify Woody as her attacker. Uncle Ralph worries about Martha's mental state, having observed that she has been depressed. At Martha's villa, Christina goes missing while playing a sort of hide-and-seek with Martha involving a blindfold. She is shortly after discovered dead near the house, and it is determined she was strangled to death. Christina's murder prompts police to reopen their investigation, and Woody is ultimately acquitted of his charges when an autopsy proves that his girlfriend, the girl in a ditch, died of a heroin overdose. Uncle Ralph soon after succumbs to a heart attack and presumably dies, only to be revealed as alive later without Martha's knowledge.

Martha is left alone at the villa one night, and finds herself again presumably being stalked by an assailant. She flees to the nearby cemetery and finds a pistol to use inside a crypt, only to find her chauffeur Marcos was following her. She is confronted by police officers, Dr. Laurent, and Uncle Ralph. Laurent informs Martha he filled her gun with blanks, and that Martha has been committing the murders all along in a dissociated state: Martha killed Jenny out of jealousy of her singing voice, then subsequently killed Annie in the woods to divert suspicion from her. She then strangled Christina to death when the girl had discovered evidence linking Martha to the crimes: the Snoopy necklace was found in the woods, and Uncle Ralph read Christina's diaries that said she found it covered in blood without knowing how it related to the murders. As Martha is escorted away, she regains her speech for the first time since childhood, and begins reciting the Lewis Carroll poem "The Mouse's Tale", which she once performed for her schoolmates as a child and listened to in tapes throughout the film.