Silje, Markus, and Bendik call themselves tower agents and have their secret club room at the top of the old church tower. Just before Christmas, the scary Klausen takes over as the church bell ringer. He burns the script for the children's Christmas play and plans to steal the money that will be collected on Christmas Eve. The tower agents discover what is about to happen and take action. Unexpectedly, they receive help from a mysterious key that allows them to travel 2,000 years back in time. They meet Mary and Joseph, the wise men, and others who put them on the trail of a new Christmas play. Now they must act quickly.
