In an affluent gothic household, the eccentric Addams family welcomes a new addition to their family—baby Pubert. Concerned with the baby's well-being amidst the siblings' dangerous play, the parents decide to hire a nanny. After several failed attempts, they hire Debbie Jellinsky, a seemingly perfect caretaker with a sunny disposition. What the family doesn't know is that Debbie has a hidden agenda.

Meanwhile, the Addams children, Wednesday and Pugsley, are sent to a summer camp after their attempts to harm their new sibling become too much for the nanny to handle. At camp, the siblings' morose and macabre demeanor immediately sets them apart from the other chipper campers. As they navigate the perky environment that starkly contrasts with their own dark tastes, Debbie sets her plan into motion in the Addams household.