On a remote Turkish island, the vampire Countess Nadine Carody Soledad Miranda lures unwary victims with a sultry nightclub act and sets her sights on Linda, a young American woman working in a legal firm in Istanbul. Linda Westinghouse Ewa Strömberg begins dreaming about Nadine and makes plans to reach her home on the island, even as Memmet Jesús Franco warns her not to go. Undeterred, Linda follows Memmet to his chamber, where she unexpectedly witnesses him torturing a young woman. She barely escapes that claustrophobic moment and heads toward Nadine’s domain, where the two women finally meet.
The two swim together while Nadine remarks that the house where they’re staying once belonged to Count Dracula. After Linda starts to feel dizzy from wine, Nadine leads her to a private room where their attraction deepens: they have sex and Nadine draws blood from Linda’s neck. The following morning, Linda discovers Nadine motionless in a swimming pool and faints.
At the hospital the next day, Agra [Heidrun Kussin] appears in mental distress, claiming visions of Nadine. She is under the care of Dr. Alwin Seward [Dennis Price], who also tends to Linda, who cannot remember the incident with Nadine. Back at Nadine’s home, Nadine returns in person and recounts to Morpho [José Martínez Blanco] how she became a vampire and her fixation on Linda, who she longs to turn into a fellow immortal. Nadine uses her powers to reach Linda, urging her to come back to the island, where the two once again drink blood and share intimate moments.
Back in the asylum, Dr. Seward reveals a chilling truth: his interest in Linda was not entirely protective. He admits that he only tried to lure Nadine closer to him so he could become a vampire himself. Nadine refuses this alliance and commands Morpho to kill him. As Omar [Andrea Montchal] searches for Linda, Memmet warns Linda that all women who return from the island tend to descend into madness, a fate that has driven him to murder several women around the area—his own wife Agra among them.
Linda eventually fights back, killing Memmet with a saw and escaping to find Nadine. She locates Nadine at her home, nearly dead and desperate for blood to survive. Linda rejects Nadine’s plea, bites her neck, and drives a pole through Nadine’s left eye to end her life. Morpho then commits suicide, and Omar finds Linda, trying to persuade him that the entire ordeal could have been only a dream.
