In Halloweentown II: Kalabar's Revenge, Marnie Cromwell is now a teenager and feels frustrated that her mother won't let her use her magic powers. She is excited to learn that her grandmother Aggie has come to visit them in the real world and is planning to take them with her to Halloweentown for the annual Halloween celebration.
However, things start to go wrong when they arrive in Halloweentown. The town is grey and dull, the creatures are unhappy and their magic powers are disappearing. They soon learn that Kalabar's son, Kal, wants revenge for his father's defeat in the first movie and plans to use the grandmother's magic book to transform Halloweentown into a realm similar to the real world.
Marnie and her siblings, Dylan and Sophie, join forces with their grandmother, her old flame, a skeleton taxi driver, and other creatures from Halloweentown to stop Kal's plan. They must find a way to restore the magic and happiness to Halloweentown before it's too late.
In the process, Marnie learns the importance of embracing her magic powers and using them to help others, while her brother Dylan learns to appreciate the value of his own unique abilities. Together, they save both Halloweentown and the real world from Kal's wrath.