Brødrene Mortensens jul

14-year old Wilhelm, who hates Christmas, and his younger brother, 7-year old Hugo go on an adventure to find "J.N." who keeps sending letters to Hugo. Hugo thinks it stands for "Julenissen" (The Christmas Elf, another name for Santa Claus), but Wilhelm insists it's not. With the help of their friends, Birthe and Mouritz, they go on the search to find the person behind those letters. Meanwhile, Wilhelm struggles with his feelings for the girl working in the local coffee shop and trying to get her affection.