TV horror hostess Elvira, Mistress of the Dark quits her job after the station's new owner sexually harasses her. She plans to open an act in Las Vegas, but needs $50,000 for the project. Upon learning she is a beneficiary of her deceased great-aunt Morgana, she travels to Fallwell, Massachusetts, to claim the inheritance, which includes a mansion and Morgana's pet poodle, Algonquin.
In Fallwell, Elvira's worldly attitude and revealing clothes set the conservative town council against her. But theater operator Bob Redding befriends her. The town's teenagers quickly accept her, to the chagrin of their parents, who consider her a bad influence. Bowling alley owner Patty is interested in Bob, and with help from members of the school board and the PTA, she humiliates Elvira by sabotaging the late-night film festival she was presenting at Bob's theater. Elvira struggles to sell the house, so she can depart for Las Vegas. Meanwhile, she is unaware that her seemingly-harmless uncle Vincent is actually a warlock who is obsessed with obtaining Morgana's spellbook; he plans to kill Elvira and conquer the world, and has been fuelling the townspeople's hostility.
Elvira tries to impress Bob with a home-cooked dinner, but mistakenly uses the spellbook as a cookbook and summons a creature that attacks them. Elvira learns that the book was her mother Divana's spellbook, and that Morgana hid her to protect her from Vincent. When Elvira tries to unleash the creature against the Morality Club at their picnic, she prepares the brew incorrectly and it instead has an aphrodisiac effect; the adults remove each other's clothing indiscriminately and are arrested for indecent exposure. When Patty confronts Elvira, the resulting fistfight ends up humiliating Patty by revealing that her bra is stuffed.
Vincent leads the townspeople in arresting Elvira for witchcraft, which is still illegal in the state. They decide to burn her at the stake. The teenagers try to free her from jail, but fail and accidentally lock themselves into a different cell. Bob tries to recover the spellbook from the mansion, but is tied up by Vincent, who takes the book. Algonquin transforms into a rat and unties Bob. Elvira is tied to a stake and the fire is lit, but she uses Morgana's ring to summon rain that quenches the fire; she escapes with Bob. At the mansion, Elvira and Vincent engage in a magical battle that sets fire to the house. Elvira banishes Vincent to the underworld, while the house and all of the magical artifacts are destroyed.
The next day, Elvira prepares to leave town. The townspeople apologize for their behavior, and everyone asks Elvira to stay. She kisses Bob but, as she is homeless, she insists that she must leave. Elvira has inherited Vincent's estate, which included enough money to open her show in Las Vegas. At a Las Vegas hotel, Elvira performs a lavishly produced musical number.