- Note: This plot summary refers to the original Italian version of the film.
Rosy (Michèle Mercier), a French call-girl, returns to her basement apartment at night. She receives a series of strange phone calls. The caller eventually identifies himself as Frank, her former pimp who has recently escaped from prison. Rosy is terrified; it was her testimony that sent Frank to prison. Rosy phones Mary (Lydia Alfonsi) for solace. The women have been estranged, but Rosy is certain that only Mary can help her. Mary agrees to come over that night. Seconds later, Frank calls again, promising that no matter what Rosy does he will have his revenge. Rosy doesn't realize that Mary is impersonating Frank on the telephone. Mary arrives at Rosy's apartment and attempts to calm Rosy's nerves. Mary provides Rosy with a large knife for protection before she goes to sleep.
As Rosy sleeps, Mary writes a confession explaining that she made the calls to force a reunion, knowing that Rosy would call on her for help. While she is writing, an intruder enters the apartment. The intruder is Frank (Milo Quesada), who strangles Mary. The sound of their struggle awakens Rosy, and Frank realizes he murdered the wrong woman. Frank approaches Rosy's bed, but she seizes her knife and stabs Frank. Rosy drops the knife and breaks down in hysteria.
In 19th Century Russia, Vladimir Durfe (Mark Damon) is a young nobleman who finds a beheaded corpse with a knife plunged into its heart. He takes the blade, and finds shelter in a small cottage. Durfe is approached by Giorgio (Glauco Onorato) who explains that the knife belongs to his father, who has not been seen for five days. Giorgio offers a room to Durfe and introduces him to the rest of the family: his wife (Rika Dialina), their young son Ivan, Giorgio's younger brother Pietro (Massimo Righi), and sister Sdenka (Susy Andersen). They all await the return of Gorca, who has gone to fight the wurdalak, a living cadaver who feeds on human blood, especially of close friends and family members. At midnight, Gorca (Boris Karloff) returns to the cottage with a sour demeanor and unkempt appearance. After the family goes to sleep, Ivan and Pietro are attacked by Gorca who flees the cottage with Ivan. Giorgio chases after Gorca but only returns with Ivan's corpse. Giorgio plans to stake and behead Ivan to prevent him from reviving as a Wurdalak, but is prevented from doing so by his wife. The two agree to give their son a burial.
That same night, their child appears outside and begs to be invited in. Giorgio is stabbed by his wife while she attempts to let in her son. On opening the door, she is greeted by Gorca who bites her. Vladimir and Sdenka flee from their home and hide in the ruins of a cathedral. As Vladimir sleeps, Sdenka walks outside and finds Gorca and his family surrounding her. Vladimir awakens and searches for Sdenka, finding her lying motionless in her bed at home. Sdenka awakens and upon receiving Vladimir's embrace, she bites into his neck.
"The Drop of Water"
In 1910s London, Nurse Helen Chester (Jacqueline Pierreux) is called by the maid (Milly Monti) of an elderly medium to prepare the latter's corpse for burial. As she dresses the body, she notices a sapphire ring on its finger. Chester steals it, accidentally tipping over a glass of water which drips on the floor; she is then assailed by a fly. Chester takes the ring home to her flat and witnesses strange events. The fly returns and continues to pester her, and the lights in her apartment go out as the sound of the dripping water is heard from various locations. Chester finds the woman's corpse lying in her bed. It rises and floats toward her. Chester begs for forgiveness, but ultimately strangles herself. The next morning, the concierge (Harriet White Medin) discovers Chester's body and calls the police. The pathologist (Gustavo De Nardo) arrives to examine the body and only finds a small bruise on her left finger where her ring once was. As the doctor (Alessandro Tedeschi) announces this observation, the concierge appears distressed and hears the dripping of water.