A spy series, set in the years 1408-1410, when between the Order of the Blessed Virgin Mary (still having a large, well-trained and well-armed army) and Rzeczpospolita, tension increases and war is inevitable. The main characters are Hubert called "Black" and his friend Jaksa, spies in the service of King Władysław Jagiełło, who conduct reconnaissance in the Teutonic state and at the same time work out a Teutonic spy network operating in Poland. The leader of the Polish "counterintelligence", Father Andrzej, who reports to the Crown Deputy Chancellor, suspects the leakage of very important information of state importance. The source of the leak turns out to be Canon Dunin, whom the Teutonic Knights forced to cooperate by kidnapping his niece, Una. Black and Jaksa are tasked with finding Una, and are sent on a reconnaissance mission. Black manages to engage in cooperation a strongman known as "The Maiden", with whom they will work from now on.