Halloweentown High

Two years after the previous film, Marnie proposes bringing Halloweentown students to her mortal-world high school to foster openness. The Halloweentown Council is skeptical because of the Knights of the Iron Dagger, a fanatical anti-magic group. They agree only after Marnie bets all the Cromwell magic that the plan will succeed, with a midnight Halloween deadline. If she fails, her family will lose their magical abilities.

The Halloweentown students are transported to the mortal high school and magically given human appearances to blend in. Marnie acts as a tour guide, presenting them as from Canada. Cody begins to show romantic interest in Marnie as the school year begins.

Aggie substitutes to give cover and help the newcomers adapt. The students keep to themselves and hide in a refuge Aggie creates for them in a remote school locker. Marnie encourages them to join sports and clubs to blend in.

Marnie receives a warning from the Knights of the Iron Dagger, signaling danger to the plan. A magical incident at the mall causes the Halloweentown students to publicly reveal their true non-human appearances in public. The incident raises tension and risk.

A break-in at the secret magical locker occurs and Cassie disappears. The mystery deepens as the group’s safety is compromised.

Marnie and Cody's romance develops, echoing an unexpected romance between Aggie and the school's principal Phil Flanagan. Aggie suspects Cody is behind the trouble, while Marnie suspects Flanagan.

They learn that Phil Flanagan is the Knight mentioned in the warnings; he is the last of the Knights of the Iron Dagger. Edgar Dalloway's influence looms in the background as the deeper source of unrest.

Edgar Dalloway, head of the Witches' Council and father of a student, manipulates events to keep Halloweentown isolated and uses Flanagan to ensure the plan fails. He hopes to provoke a backlash that will close the portal, making Cromwell magic the pivotal element.

The carnival gives the Halloweentown students a stage to improve mortal attitudes by showing the monsters’ ordinary lives. The haunted house depicts creatures coexisting with humans, while Gwen uses a Witch's Glass to hunt Cassie.

Dalloway launches magical attacks by animating the haunted-house monsters, causing panic. Flanagan incites a mob to corner the Halloweentown students, but Cody tames the crowd and the students reveal themselves. The crowd accepts them, and Flanagan renounces being a knight and accepts Aggie.

The Cromwell magic is returned; Gwen returns with the imprisoned student, and the Council imprisons Dalloway in another Witch's Glass, ending his influence and reclaiming the families' magic.

The portal between Halloweentown and the mortal world opens inside the haunted house, allowing crowds of Halloweentown children to cross over to the carnival. The two worlds mingle as the celebration of coexistence begins.

Marnie flies off for a romantic broom ride with Cody, and they kiss as they soar over the carnival, sealing their relationship amidst the shared celebration.