It is decided after the battle of Brännkyrka that Sten Sture and King Christian will meet in Österhaninge for negotiations.

To guarantee the safety of the king, the Swedish side sends six men as hostages to be kept by the Danes for as long as the negotiations last.

However, Christian does not show up for the negotiations, violates the deal with the Swedish side and takes the hostages aboard ships carrying them to Copenhagen.

The six members of the kidnapped hostage are Hemming Gadh, Lars Siggesson (Sparre), Jöran Siggesson (Sparre), Olof Ryning, Bengt Nilsson (Färla)—and Gustav Eriksson.

Gustav is held in Kalø slot, a castle located in eastern Jutland, where he is treated very well after promising he will make no attempt to escape.

A reason for this gentle treatment is King Christian's hope to persuade the six men to switch sides, and turn against their leader Sten Sture.

This strategy will prove successful regarding all men but Gustav, who remains loyal to the Sture party.