Kay Caldwell [Louise Allbritton] and Frank Stanley [Robert Paige] have always been in love, even since they were children. But when Kay returns from traveling in Hungary, she seems changed. First, she begins to express a morbid curiosity with the supernatural. Then, she brings back with her a gypsy fortune teller, Madame Zimba [Adeline DeWalt Reynolds]. Finally, she has invited Hungarian Count Alucard [Lon Chaney, Jr] to be a guest at Dark Oaks, the southern plantation where Kay lives with her father Colonel Caldwell [George Irving] and her sister Claire [Evelyn Ankers].
On the night of Alucard's arrival, Kay throws a welcome party. But only Alucard's baggage arrives on the train; no Alucard. Madame Zimba warns Kay that Alucard is not who he says he is and that death looms over Dark Oaks. True to her word, Madame Zimba suddenly dies of a heart attack after seeing a bat. Later that evening, Colonel Caldwell also dies of a heart attack, and Alucard arrives at Dark Oaks.
Days later, at the reading of the will, it is discovered that Kay inherits the plantation and Claire all the money. With no resources to care for the plantation, Kay should be worried, but she is not. In fact, she admits that this is the way she wants it. In addition, Kay does not intend anymore to marry Frank and appears to be seeing Alucard, but no one can find out where Alucard is staying or what happened to the two large boxes that arrived with his baggage. Claire and Dr. Harry Brewster [Frank Craven] wonder if Kay might be insane, and Brewster calls his Hungarian friend Professor Lazlo [J. Edward Bromberg] to inquire about the legitimacy of Count Alucard. Could he really be Count Dracula?
One night Kay goes into the swamp where Alucard issues forth from a coffin buried under the water. Later that night, Kay and Alucard are married. Distraught, Frank shoots Alucard but kills Kay instead and escapes to Brewster's house. Brewster goes to Dark Oaks but finds Kay seated in bed and quite alive. Nevertheless, the next day Frank confesses to murder and, when the Sheriff goes out to Dark Oaks, they find Kay's lifeless body lying in a coffin. Frank is taken to jail, and Professor Lazlo arrives from Hungary to offer his help. As Lazlo educates Brewster about vampires, Alucard appears and confirms that he is indeed the son of Dracula. Lazlo frightens off Alucard with a crucifix, and Lazlo and Brewster set out to kill him and to cremate Kay.
That night, Kay comes to Frank in his jail cell. She confesses her undying love for him, tells him that she did this for the immortality, and offers Frank the opportunity to share immortality with her, but he must first destroy Alucard. Frank escapes from jail and sets Alucard's coffin afire. The sun rises, and Alucard is destroyed. Frank then goes to Dark Oaks where he kisses Kay's body goodbye and sets her on fire, too. [Original synopsis by bj_kuehl.]