A 300-year-old witch wreaks havoc when she falls in love with a young politician.

In the late seventeenth century, New Englander Jonathan Wooley watches as Jennifer, whom he has accused of witchcraft, and her father Daniel, burn to death at the stake, and he recalls that the beautiful Jennifer condemned him and his descendents to perpetual unhappiness in love. An oak tree is planted over the ashes to keep in the evil spirits, but the curse against the Wooleys continues for generations until, in the modern day, a lightning bolt strikes the oak tree, releasing the spirits of Jennifer and Daniel. The spirits emerge as wisps of smoke and watch a party in the nearby house at which the impending marriage of gubernatorial candidate Wallace Wooley, a descendant and exact likeness of Jonathan, to the shrewish Estelle Masterson is being celebrated. Jennifer insists that her father grant her a corporeal body and, because the transformation process requires that she be created out of fire, he ignites the Pilgrim Hotel. Wallace, Estelle and their friend, Dr. Dudley White, are detained on their way home because of the fire, and when Wallace hears Jennifer's haunting voice calling from within the burning building, he goes in and saves her. Wallace gives Jennifer his coat because she is naked, and is perplexed by Jennifer's knowledge of him. He is further shocked when he finds her in his home after having left her at the hospital. Despite her seductive entreaties, Wallace puts Jennifer in a taxi, but the mischievous witch disappears from the car and reappears in his bedroom, remaining there until the morning. Wallace's housemaid, Margaret, is shocked to find Jennifer in his bedroom on his wedding day and, while Wallace goes out with Estelle and her father, J. B. Masterson, who is also his campaign backer, Jennifer and Daniel concoct a love potion with which to ensnare Wallace. Daniel then decides to take a corporeal form and burns another building to create himself. Wallace returns but Jennifer accidentally drinks the potion and falls desperately in love with him. That day, Daniel uses some nefarious tactics to stop the wedding but only succeeds in getting drunk and arrested. Jennifer then interrupts the ceremony by pretending to collapse, but revives the instant Wallace expresses any feeling for her. Estelle finally calls off the wedding after she finds Wallace and Jennifer kissing, and her father vows to ruin Wallace's political career. While Daniel, who is too drunk to remember any of his spells, howls to be released from jail, Wallace and Jennifer marry at a small roadside inn. Jennifer confesses to Wallace that she is a witch, but he does not believe her until she uses witchcraft to ensure that he wins the gubernatorial election, even though Masterson had spread rumors of scandal that marred his campaign. Daniel escapes from jail and insists that Jennifer be punished for revealing her nature to a mortal by imprisoning her again in the oak tree. He temporarily strips her of her powers, and despite her best efforts, Jennifer is returned to spirit form. Daniel and Jennifer watch as Wallace mourns over Jennifer's lifeless body and, to Jennifer's surprise, she unexpectedly returns to her corporeal form, thereby proving that love is stronger than witchcraft. She then traps her father in a bottle of rum, which is thereafter kept under lock and key. As time passes, Wallace and Jennifer have two sons and a daughter, Jennifer, who shows early signs of having inherited her namesake's talents.