Hungarian Count Alucard, a mysterious stranger, arrives in the U.S. invited by Katherine Caldwell, one of the daughters of New Orleans plantation owner Colonel Caldwell. Shortly after his arrival, the Colonel dies of apparent heart failure and leaves his wealth to his two daughters, with Claire receiving all the money and Katherine his estate "Dark Oaks". Katherine, a woman with a taste for the morbid, has been secretly dating Alucard and eventually marries him, shunning her long-time boyfriend Frank Stanley. Frank confronts the couple and tries to shoot Alucard, but the bullets pass through the Count's body and hit Katherine, seemingly killing her. A shocked Frank runs off to Dr. Brewster, who visits Dark Oaks and is welcomed by Alucard and a living Katherine. The couple instruct him that henceforth they will be devoting their days to scientific research and only welcome visitors at night. Frank goes on to the police and confesses to the murder of Katherine. Brewster tries to convince the Sheriff that he saw Katherine alive and that she would be away all day, but the Sheriff insists on searching Dark Oaks. He finds Katherine's dead body and has her transferred to the morgue. Dr. Brewster is shown reading the novel Dracula.

Meanwhile, Hungarian Professor Lazlo arrives at Brewster's house. Brewster has noticed that Alucard is Dracula spelled backwards and Lazlo suspects vampirism. A local boy brought to Brewster's house confirms this suspicion—there are bite marks on his neck. Later, the Count appears to Brewster and Lazlo but is driven away by a cross. Vampiric Katherine enters Frank's cell as a bat and starts his transformation. After he awakens, she tells him she still loves him. She explains that she only married Alucard (who is really Dracula himself) to obtain immortality and wants to share that immortality with Frank. He is initially repulsed by her idea, but then yields to her. After she explains that she has already drunk some of his blood, she advises him on how to destroy Alucard. He breaks out of prison, seeks out Alucard's hiding place and burns his coffin. Without his daytime sanctuary, Alucard is destroyed when the sun rises. Brewster, Lazlo, and the Sheriff arrive at the scene to find Alucard's remains.

Meanwhile, Frank stumbles into the playroom where Katherine said she would be. He finds her coffin and gazes down at her lifeless body. Knowing he must kill the love of his life, Frank takes off his ring and puts it on Katherine's left ring finger. Once Brewster and the others reach the room, they see Frank appear at the door. He steps back allowing them to follow. As they enter the room, they see Katherine's burning coffin. They all stare, speechlessly, while Frank mourns the loss of his love.