In a nameless Baltic country in the 19th Century, Kurt Menliff (Christopher Lee) arrives at his seaside castle after many years of wondering through Europe. But he is not warmly received for everyone knows that he is a sadist who gets sexual gratification from whipping his lovers. His former lover is Nevenka Menliff (Daliah Lavi), who is now married to Kurt's spineless younger brother Christian (Luciano Stella). Kurt and Christian's father, an invalid Count (Gustavo De Nardo) has never forgiven Kurt for leaving in the first place. The maid, Giorgia (Harriet White Medin) is anxious to get back at him for causing the suicide of her daughter who stabbed herself in the throat after Kurt walked out on her years ago. Nevertheless, Kurt is allowed to stay because he is family.
The following morning, Kurt confronts his other cousin Katia (Ida Galli) whom he knows to be secretly in love with Christian. He smugly assures her that he feels her pain, as he is interested in Nevenka. Katia flees from this unwanted revelation. Kurt next enters the large, cavernous living room where his father spends most of the time. Kurt explains that now he has returned home, he feels that he deserves to be next in line to inherit the family estate. But the Count assures him that there is no chance of that happening. "Everything you were to inherit, you forfeited forever", he tells Kurt. "You did it yourself, with your infamy!" Angered, Kurt storms out of the living room.
Embittered by this personal defeat, Kurt goes to the beach where he sees Nevenka sitting pensively by the water. He approaches her, and reminds her their past liaisons. They kiss, and then Nevenka recoils, striking Kurt across the face wit her riding crop. He then calmly takes it out of her hand and pushes her to the ground. Cracking the riding crop across her back, he sneers: "You haven't changed, I see. You've always loved violence". He then proceeds to strike her again and again. Nevenka's reactions to being beaten are very subdued and the expression her face suggests sexual excitement. After striking her several more times, Kurt tosses the riding crop aside and proceeds to rape her.
After finishing with Nevenka, Kurt returns to the castle where he is confronted by Katia and Christian who ask him where Nevenka is, to which Kurt replies that he has no idea. They immediately know that Kurt is lying when they see him holding Nevenka's riding crop. As it is getting dark, Katia and Christian head out to look for Nevenka, as Kurt retires to his bedroom. Soon after, he is killed when an unseen person stabs him in the throat with a dagger.
Meanwhile, Christian discovers Nevenka on the beach, her back covered with welts. After putting Nevenka to bed, Christian sends out for Kurt. The family butler, Losat (Luciano Pigozzi), goes to fetch Kurt, only to discover his dead body on the floor, with the dagger lying beside him. Losat's screams bring the others into the room, where Giorgia is hysterical with joy to see him dead, killed by the same dagger her daughter used to commit suicide.
After Kurt's funeral, Christian timidly asks his father if he was responsible for the killing. The Count is enraged by these accusations, and tells his son to leave the living room. Soon after, the entire family unit begins to unravel. The marriage between Christian and Nevenka becomes more strained. Nevenka starts to see visions of Kurt. At one point, his ghost visits her in the middle of the night, whipping her more ferocious than ever.
Soon afterwards, the Count is found murdered in the living room in the same fashion as Kurt, with the same weapon. Christian vows to find the killer, and Katia accuses Giorgia, pointing out that she had every motive to kill Kurt. Giorgia admits that she wanted to kill Kurt, but assures everybody that her love for the Count would have made it impossible for her to kill him. Elsewhere, Nevenka's mind becomes more unhinged and each nightmarish vision of Kurt unsettles her ever further. After explaining everything to Christian, even he comes to believe that Kurt may have been behind the murder of their father, and that his ghost is doing all the killing.
Christian and Loast unearth Kurt's decaying dead body from the family crypt and burn the remains to try to put Kurt to rest. As they watch Kurt's remains burn, the dead man's sinister laughter rings out. Following a cloaked figured dressed as Kurt, Christian and Loast follow it to the castle where Christian pulls off the hood to reveals none other than Nevenka. At last the terrible truth comes out: Nevenka was the one who murdered Kurt after sneaking back into the castle and sneaking out through hidden passageways. But at her remorse over the crime, coupled by the realization that she really did love Kurt, compelled her to act out as if he is still alive, by dressing in his clothes to complement the illusion. Nevenka even went as far as to whip her self during those nights, and murdered her father as revenge for his ostracizing her love.
Nevenka escapes from her husband, stabbing him in the arm in the process, and makes her way back to the crypt. Now really believing that Kurt is alive, Nevenka decides to put a stop to it all by killing him again. Kurt appears to her for a final time where in their final 'embrace' she stabs him, but instead stabs herself in the chest with the dagger, and she falls dead.