Martin (John Amplas), a young man who looks around 20-years-old, boards a train in Indianapolis, Indiana for New York. At night, he breaks into a sleeping car and sedates a woman with a syringe full of narcotics. She struggles, but he tells her not to struggle or be upset because she won't feel pain. After a few minutes, the woman falls asleep, and Martin has sex with the unconscious woman. Afterwards, he slices her wrists with a razor blade so he can drink her blood. The woman bleeds to death in her sleep.In the morning, the train stops in Pittsburgh, Pennsylvania where Martin disembarks. He is met by Tata Cuda (Lincoln Maazel) an elderly and hostile old man wearing a white suit who claims to be his cousin from the Old World. Together, they travel by another train to the town of Braddock, a dying industrial suburb. They walk to Cuda's large house where he shows Martin his living quarters. Cuda then accuses Martin of being an 84-year-old vampire from his old country. He has taken in Martin because he is family since Martin's parents are said to have recently died, but tells him, "First I will save your soul. Then I will destroy you." Cuda tells Martin that he is free to come and go as he pleases, but he also threatens to destroy Martin without salvation if he kills a single person from the neighborhood, also adding his granddaughter, Christina (Christine Forrest) lives with him.Martin chases Cuda to his own room, busts open the door, forcing Cuda to grab a crucifix from his dresser drawer and defend himself with it, whispering "Nosferatu". Martin denies being a vampire and states that he is merely Cuda's cousin. Martin then grabs a string of garlic on Cuda's door, bites it and grabs the small, white crucifix Tata Cuda aims at him. Martin holds the cross gingerly to his face, saying bitterly, "It isn't magic... even I know that. It isn't magic".That evening, Cuda introduces Christina to Martin, but also warns her to stay away from him. But Christina instead strikes up a friendship with Martin who confides in her about his vampire heritage. When Cuda later confirms Martin's claims to be a vampire, Christina, not surprisingly, refuses to believe either one. She thinks that Cuda and the other members of her family have driven Martin to insanity by making him think that he is a vampire. (It is never revealed if Martin really is a vampire, or just a shy and lonely youth with troubled issues.)Christina is the only person that Martin gets the courage to talk to. When Christina's boyfriend Arthur (Tom Savini) arrives at the house for dinner, Martin stops talking and backs away despite Arthur's casual attempt at a conversation. Christina later confides in Martin that she hopes to leave Braddock someday with Arthur, even though Martin points out that Arthur treats her badly and is both verbally and physically abusive towards her.When Christina sees that Martin won't talk to anyone else, she buys him a phone which he installs in his room. Martin begins to repeatedly call a radio talk show where he describes what it's like to be a vampire. He becomes known on the radio as "the Count" to all the listeners. But the patronizing host (voice of cameraman Michael Gornick) thinks he's just crazy.Martin gets a job at Cuda's grocery store, stocking shelves, hauling boxes around, and even gets to be a delivery boy for some of the customers. One of his customers is a certain Abby Santini (Elyane Nadeau), who becomes taken with Martin. She is a very friendly young woman who is depressed who tells Martin that her husband is unfaithful. But Martin still does not have the nerve to talk with her. Nonetheless, she is happy to have someone to confide in with her life problems. Martin phones the radio show host to describe his infatuation with the housewife and senses that she wants to have sex with him. When the radio show host asks Martin if it is a sexual problem that he has involving women criticizing him during sex, Martin replies that he has never had sex with a woman who was awake.One day, Martin travels by train outside of Braddock to look for victims. At a supermarket, he follows a young woman (Sarah Venable) home to her posh suburban house. He sees the woman's husband, Mr. Willard, (producer Richard Rubenstein) leave for a long business trip, and Martin decides this would be the right time for more feeding. Martin returns to the house after dark and programs a walkie-talkie to open the garage door on an open frequency.Throughout the sequence, Martin begins 'remembering' the distant past, in black-and-white: possibly he was a vampire on the hunt, killing a young romantic victim, then chased by an angry horde armed with torches and pitchforks, or he has seen one monster movie too many. Open ended.Back in the present, Martin is in the house intending to surprise and attack the housewife whom he believes her to be alone. But it's Martin who gets the surprise when he bursts into the bedroom to find the housewife in bed with her adulterous lover Lewis (porn star Al Levitsky). After a vicious struggle, Martin jabs both of them with hypodermic needles full of narcotics, and waits for the drugs to take affect. He drags the unconscious body of Lewis from the house to a small forest on the other side of a low fence, and down a hill, where he kills him by shoving a broken tree branch into his neck, and drinks his blood. Martin returns to the house where he has sex with the unconscious woman. But out of compassion and pity, he decides to let her live. He then removes any evidence of his presence with practiced, methodical precision.After one Sunday at church, attended by, among other people, Abby Santini and her philandering husband, Cuda brings home Father Howard (director George A. Romero) who asks him about the possibility of exorcism and demon possession. Father Howard calls upon the elderly Father Zulemas (Clifford Forrest, Jr.) over at Cuda's request. Together, Cuda and Zulemas confront Martin his bedroom and attempt to perform an exorcism on him. At this point, Martin remembers (another real or imaginary flashback), in the Old Country, people trying to perform an exorcism on him, and fleeing. Martin then flees from Cuda and Zuelmas as well.A little later that night, Martin terrorizes Cuda in a children's playground when he puts on a Dracula cape and puts false fangs into his mouth to pretend that he really is a vampire, thus humiliating the old man who takes on Martin in single combat, holding his crucifix while Martin playfully japes him. Then Cuda attempts to conquer him with his walking cane, whereupon Martin spits out his falsies, wipes makeup from his face, holding it out for Cuda to see, and states, 'It's just a costume... It's only a costume," then drifts away into the night mist.One day, Martin finally musters the courage to talk with Abby during a routine delivery to her house where he tells her that he's aware of her attempts to seduce him and wants now to have sex with her. After having consensual sex for the first time, Martin learns that a tearful Abby is extremely depressed because her husband just left her after she discovered that she cannot bear children, and that her desires towards Martin are based on sex and nothing else. But Martin wants to stay with her and help her move on with her life. Martin tells the radio show host about his affair with the housewife and that he no longer has the urge to attack other women.Meanwhile, Arthur meets with Cuda in a bar and tells him that he wants Christina to leave town with him to New York City so they can get married and start a family. Martin later meets Christina on the front porch, where she's put out about Arthur apparently forgetting they were going out that night. Martin finally voices his dislike of Arthur, stating, "I don't like Arthur, he makes you feel bad," after which Christina complains about her current life and goes back inside. But Christina becomes angry at Cuda when she learns that he told Arthur that insanity runs in their family and he shouldn't consider having children with her. After confronting her grandfather, he slaps her for blaspheming, twice.Shortly afterwards, Christina packs up and leaves Braddock with Arthur, despite Martin telling her that Arthur is abusive towards her. But her mind is made up. Before leaving, Christina tells Martin that she really has no ill feelings towards him and just wants to make a fresh start with her life. She says goodbye to him and promises to write. But Martin knows that with an abusive and possessive man in Christina's life, she probably won't (Martin turns out of be rightfully so; Christina never calls or writes ever again). With no one to cook for him now, Tata Cuda has to do it for himself and Martin, which is only the tip of a slowly melting iceberg, including Martin now stalking a verbally-abusive Mrs. Bellini, a local neighbor and regular grocery store customer, with an eye toward making her pay for her insolence.Depressed over losing his one true friend, Martin phones the radio show host and tells him that he's getting "shaky" and wants to go out looking for more victims. That night, Martin travels to a rough crime-ridden area of Pittsburgh and attacks two derelicts (Tony Pantanella and Regis Survinski) in a junk and grime-filled storage building. He kills both of them by beating them viciously with a steel pipe, then slitting one bum's wrist and drinking his blood. Martin runs and breaks into a second-hand store full of items to change his blood-splattered clothing. Just then, a police car shows up and two cops get out. Martin narrowly escapes during a long chase on foot which leads from the store, through the garbage-strewn streets and into an old warehouse where a drug deal is going down. A shootout between the two cops and three thugs ends where all of them are killed, leaving Martin as the sole survivor who hurriedly runs away from the carnage.The next day, after shopping for poultry with Cuda, Martin finds Abby Santini dead in her bathtub, after she has slit her writs with a razor blade and swallowed booze. After calling the police to report the dead body, he phones the radio show host later that afternoon to say that he didn't kill her and really doesn't need friends or people to talk to for he is his own person.After joining a town parade with a marching band, Shriners-types, and other kids, Martin calls the DJ one final time, believing his life all about to get better. But Cuda has heard about Abby's suicide, mistakenly thinking Martin killed her and made it look like a suicide as he's done before. The next morning, Cuda walks into Martin's room while he is asleep and kills him by hammering a wooden stake through Martin's heart.Cuda buries Martin's body in his back garden, while over the closing credits various voices from people are heard talking to the radio show host asking the whereabouts of "the Count".