Debbie Reynolds is Aggie Cromwell, the peppery grandmother to typical American kids Marnie (Joey Zimmerman), Dylan (Joey Zimmerman), and Sophie (Emily Roeske). During her annual visit to their mother, Gwen (Judith Hoag), she reveals that she is a benevolent witch, and that Gwen and her family all have latent magical powers. Whisking the kids off to Halloweentown, she subsequently does battle with evil forces conjured up by Gwen's old flame, Kalabar (Robin Thomas), a warlock with delusions of grandeur and a nasty habit of transforming children into zombies.