At the end of the 13th century, the border area of Göra älv, was a dark and chaotic time. The Swedish king, Birger Magnusson, had two brothers, the dukes Erik and Valdemar. They have large tracts of land, but are both jealous of their brother Birger’s position as king and conspire to oust him from the throne.

To increase his power, brother Duke Erik, travels to Norway and requests the hand of the Norwegian princess Ingeborg Håkansdotter. At that time she was only one years old! Duke Erik himself was 20. The Norwegian King Håkon V Magnusson agreed to the engagement and the alliance with Norway became history. Duke Erik now receives the old Norwegian Viking town Kongahälla and the associated castle on Ragnhildsholmen as a grant from the Norwegian king and future father-in-law. Kongahälla, at the time, was located 3 kilometers west from Bohus.

Duke Erik still had big ambitions to take over the crown in Sweden. The year is 1306 and at the royal estate Håtuna in Uppland, the two brothers now go so far that together they attack their own brother, King Birger, and keep him prisoner for 2 years. To become free, Birger is forced to relinquish power over Sweden to his two brothers. But now, something is about to happen that the two brothers did not expect!