JK and the Wooden Owl, follows twins Jesper and Heather Knasfis who, while staying at their grandmother Maisie's farm, discover a mysterious wooden trunk in the attic containing a hidden treasure map. Their quest leads them to the forest of Rold in Denmark, where they must navigate local legends and outsmart a menacing woodcutter to find a buried strongbox. Although the box appears to contain worthless rags, it eventually reveals a valuable historical hoard, resulting in a tense encounter with the police regarding national treasure laws.