On the night Ronja was born, thunder rolled over the mountains. Yes, it was a stormy night that even made all the creatures hiding in the Mattis Forest retreat in fright. In the middle of the forest, at Mattisburg, surrounded by robbers, gray gnomes, Rumpelwichten, and wild drudges, Ronja, the daughter of the robber chief Mattis, grows up. One day, during her adventures, she meets Birk, the robber's son from the rival clan of Borka. Her parents forbid them to see each other, but Ronja and Birk stand together. A summer full of joy and sorrow, freedom, danger, and adventure begins in the Mattis Forest.