The introduction of the story depicts a small apartment in an impoverished area of Sweden, where Skorpan is bedridden with tuberculosis and, the reader is given to understand, unlikely to survive. Jonatan seeks to comfort his little brother by telling him about Nangijala, a land beyond death, where there are "sagas and campfires". Jonathan dies while saving his brother from a fire, by jumping with his brother on his back out of a 3 storey building, leaving his brother alone. Soon after, Skorpan dies from his disease, and is reunited with Jonatan in Nangijala, where he, too, will be named Lionheart. The brothers experience adventures: together with a resistance group, they join the struggle against the tyrant Tengil, who rules with the aid of the fearsome fire-breathing dragon, Katla. These adventures form the greater part of the book.