While frolicking in the forest near her home, the irrepressible Ronia (Hanna Zetterberg) meets Birk (Dan Hafstrom), a charming and impish young boy, and the new friends set off on an adventure across the sprawling countryside. Unfortunately for Ronia, Birk is the son of Borka (Per Oscarsson), the sworn enemy of her father, Mattis (Börje Ahlstedt). When the rivals hear of their children's friendship, Ronia and Birk decide to hide until their families put aside their differences.