Barnabas Collins appeared at Collinwood, the Collins ancestral estate, claiming to be a cousin from England, the last of his line. Due to his uncanny resemblance to the portrait of the 18th century Barnabas, Elizabeth Collins Stoddard, the mistress of the house, had no reason to doubt his story. He was readily accepted by the family. Preceding his arrival, however, many bizarre events occurred. After deciphering clues to the whereabouts of some missing ancestral jewels, the Collins' surly handyman, Willie Loomis, came upon a chained coffin hidden in the family crypt. But once he'd broken into it, he found more than he'd anticipated. That same evening, Daphne Budd, the Collins' secretary was brutally attacked. She was found unconscious with a savage bite wound in her throat. And the next evening, a woman was found strangled with the exact same type of wound. Both women had lost an extraordinary amount of blood.
Once the family agreed to Barnabas' request to settle into the Old House, the original family home, he, along with his new servant, Willie Loomis, proceed to restore the long neglected, dilapidated building to it's former glory. Carolyn Stoddard, Elizabeth's daughter, becomes particularly fascinated by her new cousin's activities. However, on the eve of a costume party honoring his arrival, Carolyn finds out Barnabas' secret when he appears in her room and attacks her. Barnabas Collins is a vampire, immortal, and two centuries old.
Despite Barnabas' attack upon her, Carolyn falls in love with him, neglecting her fiance, Todd. But when Barnabas spies Collins' governess, Maggie Evans, at the party, he is instantly mesmorized by her because she reminds him of Josette du Pres, his great love from the 18th century whom he lost. To complicate matters further, Maggie is in turn in love with Jeff Clark, a local artist. When Carolyn, insanely jealous of Barnabas' attraction to Maggie, threatens to reveal that he is a vampire, Barnabas savagely attacks her, and her lifeless body is found slumped at Collinwood's entrance.
After her funeral, Carolyn returns from the dead as a vampire and attempts to attack young David Collins. Roger Collins, David's father, is astounded and revolted that David, who is fond of pulling pranks, would invent such a tale. That is until Todd, having gone to Carolyn's grave, is later discovered after having been attacked by her. With the help of Professor T. Eliot Stokes, the family concludes that Carolyn must be found and destroyed, so they use Todd to lure Carolyn into the open. When Todd escapes, Stokes and the authorities track him to Collinwood's stable, where Carolyn is cornered, and Stokes drives a stake into her heart.