David Winter composes soundtracks at his home, Woodstock farm. During a thunderstorm his dog becomes agitated and he lets it outside. The horse in his stable sounds disturbed by something, so he checks it out. What he discovers is a young woman lying on the straw beneath a black shawl. She claims to be Lucinda Jessop, a witch born in the year 1627.
She explains to David that a puritan gang tried her by fire and water but that she escaped them by transporting herself through time.
David locks her in the bedroom and telephones his doctor, Charles, to come over and inspect her. When Charles arrives, Lucinda has disappeared. His doctor believes he has been hallucinating, caused by overwork and the pills he has been taking.
When Charles leaves, David goes back to his bedroom and finds Lucinda has come back. She uses her wiles to seduce him into bed.
Charles contacts David's wife, Mary, and informs her of the situation. She tells him that she will visit him the next morning and stay with him for a time.
When Mary arrives to stay at David's, he tells that her Lucinda is not just a figment of his imagination. Three weird occurrences then happen: a dead bird is found on the bed, a bath fills up with blood and Mary is nearly hit by a falling statuette. Mary prepares to leave thinking David is the root cause of all these events. Packing her bags, the clothes in her cupboards are suddenly flung upwards in a huge wind. Mary realises that David may be right and that supernatural forces may be present.
Mary makes the decision to see the local vicar to ask for his help...
Mary and the vicar look through old church records and discover an entry detailing Lucinda Jessop. She managed to escape the witch trials but then vanished. Mary gallops home but Lucinda steps out in front of the horse causing Mary to dismount. Waking up, Mary finds herself in hospital with horrendous pains down her left side.
Mary returns home to a completely wrecked bedroom. A voodoo doll lies on the mantlepiece with knives along its left side. Mary pulls them out one by one and then goes to find David. Mary is then locked in the cellar by David who then prepares a large fire outside.
Mary escapes from the cellar and during a struggle, Mary manages to lock David in the barn. When she turns around Lucinda is standing there. Mary remakes the voodoo doll into Lucinda's effigy and tries to throw it into the fire, but Lucinda stops her. Mary then discovers that Lucinda is afraid of water and throws a bucket of water over her. The two women struggle and Mary forces Lucinda into a water trough where she is drowned.
Mary opens the barn door and lets David out of the burning building. The voodoo doll is thrown onto the fire - Lucinda screams.