The action of the season covers the years 1376-1399. After the death of King Casimir, fights for the Polish throne begin. He is succeeded by his nephew, King Louis, who also has no son. His youngest daughter Hedwig becomes the ruler of Poland. Polish nobles force her to marry Jogaila, Grand Duke of Lithuania. The Polish-Lithuanian union is established.

Two years after the death of Queen Aldona, King Casimir remarries. His second wife become Queen Adelaide of Hesse. The season, covering the years 1342-1374, shows their unhappy and childless marriage and the bigamic ties of King Casimir with Christina Rokiczana and Princess Hedwig of Sagan.

The first series presents the events of 1325–1339, showing the last years of the reign of King Władysław Łokietek and the beginnings of the reign of Casimir the Great. It focuses mainly on the king's first marriage with Queen Aldona of Lithuania and on the relationship with his mother, Queen Hedwg. It shows the first moments of the reign of young Casimir, the marriage, relations with Lithuania and Hungary, as well as the diplomatic policy of the Kingdom during the reign of the young king, Visegrad congresses and the conflict between the King and Bishop Grot.