The night that Ronja was born, lightening hit Matt's fort and split it in half. Since then, Matt's robbers keep to the southern part of the castle. Helvetesgapet, the gorge between the two parts of the castle, is a place Ronja has been told to stay away from since it is deep and dangerous.

Ronja lives a real robber's life in the castle with her father Matt, mother Lovis and all Matt's robbers. One day, the Borka robbers move into the other part of the castle. The Borka family and the Matt family have been enemies since time immemorial, so when Ronja and Birk meet each other, it is the start of a complicated friendship.

Ronja and Birk meet every day and explore a world of adventure together. They usually stay close to the castle, so if you keep an eye open, you may see them.