Set in the year 805, the series follows the everyday trails of inhabitants of an Early Middle ages principality, which is ruled by the title character Mrkomir (Goran Navojec).
Mrkomir, a Croatian duke who rules the principality, is incredibly ambitious but also foolish, which frequently brings him to ruin.
Although he is illiterate, he pretends to be literate and relies on Slavomir, who holds several important positions at the palace, including head of the secret service KOA (the Duke's operational agency), advisor, and cupbearer.
Slavomir frequently expands his riches and power by taking advantage of his position and Mrkomir's faith in his judgment.
But Mrkomir's greatest issue is that he is a vassal of the Franks, and he longs for independence so that he can fulfill his lifelong desire of becoming king and turning his principality into a kingdom.