Except for their grandmother, who lives in Halloweentown, a location where monsters go to escape reality, the Cromwell family lives in the actual world. However, the grandson of the Cromwells' long-time adversary Kalabar has devised a scheme to use the grandmother's book to change Halloweentown into a dark, gloomy imitation of the actual world, while transforming the inhabitants of the real world into monsters, as described in the book.