Heidi has moved with her two children to a new job as the manager of the city's historical center. She is moving into the old house that was offered with the position. The house has been vacant for a while and is in need of repairs, but it has also been a crucial part of the city's Christmas celebrations in the past. In her new role, Heidi takes on the task of reviving both the center and the house and is joined by David, who used to be in charge of the historical center and is still working there. Initially resistant, David gets drawn into the projects. Soon, Heidi's children also discover mysterious clues in the house and embark on a treasure hunt.