It is the year 1391. The infamous privateer Klaus Störtebeker has an extraordinary mission: Armed with a letter of marque from the Hanseatic cities of Rostock and Wismar, he is to plunder Danish ships alongside his 'Vitalienbrüder.' But that's not all: The stolen provisions are meant to supply the residents of Stockholm, as the city is under siege by the Danes. However, as the Hanseatic cities negotiate a peace treaty with the Danes, the pirate deviates from the course and pursues his own plans. What could he possibly be up to?.