Young Ronja learns to protect herself from the dangers of the Mattis Woods while Borka and his robbers cause Mattis trouble.

At Hell's Mouth, Ronja unearths a disturbing secret about the Borka robbers. In the village, Halvert is under pressure to make the forest safe.

Ronja learns something shocking about the robbers' way of life, while Mattis recruits a new member for the clan. Birk and Ronja meet again.

Ronja and Birk secretly spend their autumn days together in the forest, while Mattis creates obstacles for Borka. Cappa has a new plan.