In 1630 Russia, Princess Asa (Barbara Steele), a beautiful, dark-haired, young woman is condemned for practicing witchcraft. The grand inquisitor is none other then her estranged brother, Prince Vajda, who renounces his ties to his sister. As the executioner ties her down to the stake, Asa defiantly swears retribution by returning from the dead one day. The executioner positions a spike-lined metal mask over her face. On her brother's command, a swift hammer blow drives the mask into her skull, killing her instantly. She is then interred in the family crypt in a coffin equipped with a window, thought which the sign of the cross is visible. With the cross forever visible to her lifeless body, it is said that the witch will never return to life.200 years later, Doctors Kruvejan (Andrea Checchi) and Gorovek (John Richardson) are riding in a carriage from St. Petersburg to Moscow on their way to a medical conference. A wheel on the carriage slips out of its socket. Leaving the driver to repair the damage, the pair decide to investigate an old ruined chapel nearby, where they discover the witch's coffin in the crypt below. Kruvejan is suddenly attacked by a large bat, and when he beats it to death in his cane, he accidentally smashes the stone cross position over the window. The fragments from the cross smash the glass, enabling Kruvejan to pull away the witch's mask. Her face is sunken and decayed, but is otherwise intact. Gorovek convinces his friend to leave before the driver becomes overly anxious, but unbeknownst to both, blood from a small cut on Kruvejans hand is already working to revive Asa.Outside the chapel, the two doctors are startled by Princess Katia (Barbara Steele in a dual role), the daughter of Prince Vajda (Ivo Garrani). Gorovek is immediately smitten with her. The sad, seemingly fixed expression she wears tells of an unhappy nature, which is bourn out by her saying that the chapel is her father's property and he refuses to fix it up.The men continue their journey, stopping for the night at a small inn not far from the Vaja estate. Meanwhile in the castle, Prince Vajda is uneasy. He reminds her servant Ivan (Tino Bianchi), that this day marks the 200th anniversary of Asas execution. On this same day, every 100 years, mysterious events have happened in the area and the nearby village. The prince fears for Katia's safety, particularly since her resemblance to Asa seems to mark her for a very special fate. Ivan puts his master at ease, reminding him that so long as he wears a cross, no harm can befall him.In the crypt, the witch completes her resurrection. Using her special powers, she calls her lover, the vampire Javutich (Arturo Dominici) from his grave in the village cemetery. The vampire slowly crawls out of the earth and proceeds to act on Asa's instructions. Javutich arrives at the inn and fetches Dr. Kruvejan, claiming that the prince has called for a physician. Upon arrival at the castle, the doctor is led to a downstairs chamber. To Kruvejans astonishment, the chamber leads directly to the old crypt, where he is locked in. Kruvejans fear turns to hysteria when Asa emerges from her coffin and calls out to him. She places him under her power saying that a few drops of his blood brought her back to life. All of it will give her the strength to accomplice her vengeance. She bites him on the neck and begins to feed off his blood.Back at the castle, the prince sleeps fitfully. He is awakened by the intrusion of Javutich, who makes his way slowly to the old mans bed. The prince wakes up and is saved by the crucifix necklace he has around his neck. As Javutich retreats, Katia and her older brother Constantine (Enrico Oliveri) arrive in the bedroom responding the princes cries. But when he tells them about an intruder, Katia and Constantine think his delirious and send out for a doctor. It is Kruvejan who arrives to help him. The doctor's appearance is changed for his hair is grayer, and expression and attitude much crueler. Kruvejan successfully puts the prince into a deep sleep with some sedatives, and persuades Katia and Constantine to go to bed for the night, but persuades them to remove the crucifix from the prince's neck. Afterwards, Kruvejan reenters the prince's bedroom, and kills the old man by biting his neck and feeding on his blood.The next morning, Katia and Constantine are grief-stricken when they find their father dead. Finding that Kruvejan has disappeared, they send out for Gorovek. Yet Prince Vajda is not the only person to die mysteriously. That same morning, some village children find the dead body of one of the prince's servants on a river bank. When local people soon learn about this, they become convinced that the witch has finally returned from the grave.Meanwhile, Gorovek is amazed to learn that Kruvejan has disappeared, and refuses to believe that he would have willingly left a sick man unattended. Together with Constantine, he sets out to discover the truth. At the same time, his infatuation with Katia blooms into a full-blown romance.In the village, talk begins to circulate about the return of the witch Asa and her vampire lover. Gorovek becomes intrigued by the talk and seeks the aid of the parish priest, who assures the young man that such creatures do exist. Gorovek and the priest go to the old cemetery where Javutich is reputed to be buried, only to discover his half-buried coffin, and Kruvejan lying asleep in it. The priest slays Kruvejan by driving a wooden stake into his right eye. Gorovek hurries back to the castle to see if Katia is all right.At the castle, Javutich murders both Ivan, and then Constantine with little difficulty, leaving Katia all alone in the castle. When the princess goes to visit her father's coffin in their living room, the prince rises up from it as a vampire and advances towards her. But Javutich shows up and hurls the undead prince into the fireplace where he burns to death. Javutich then grabs Katia and takes her down into the crypt where Asa is waiting for them. Asa is still very weak and in need of more blood, grabs Katia and begins to feed off her. It is Asa's intention to murder Katia and to assume her identity in the process.Gorovek finally arrives at the castle and immediately engages in a drawn-out fight with Javuitch. Eventually the doctor dispatches the vampire the throwing him though a trap door in the floor of the path to the crypt and the vampire lands on wooden stakes at the bottom. Gorovek makes his way into the crypt, interrupting Asas rejuvenation. However, he believes the witch's claims that Katia, who is lying unconscious on the coffin, is the witch because of her pail appearance by her loss of blood. As Gorvoek prepares to drive a wooden stake into her heart, he suddenly notices that the 'witch' is wearing Katia's crucifix necklace, something impossible for an evil entity to wear a holy symbol. Immediately, Gorovek turns to Asa and tears away at her robe, revealing that her body, still undeveloped, is a putrid mass of flesh and exposed bone. Just then the priest arrives with a mob of townsfolk where they grab Asa, and they finally put the witch to death by tying her to a stake, setting it afire and she finally burns to death. As the witch finally dies, Katia arises with her life energy restored.