The father of the Olsson family is responsible for many people's not being able to receive any TV broadcasts. Therefore, the family escape to an old castle in the country, to celebrate their Christmas there, away from all angry people and dangers. However, the three children soon discover that something's not right in the old castle. It seems haunted and it bears a centuries old secret. Many comical situations occur when the children try to investigate the haunting, but the parents don't understand what's going on.