After brothers Jonathan and Crusty pass away, they reunite in Nangijala, the land of eternal spring. Casting a long shadow over their world is the tyrant Tengil, ruler of the country Karmanjaka, where he’s building his new fortress up in the Ancient Mountains.

Svante is a young boy who lives with his family in a Stockholm apartment. One day he meets Karlsson, a chubby little man in the prime of his life, who can fly using a propeller on his back and who lives in his little house on the roof.