Mid 17th century, the threshold and beginning of the Russian-Polish War. The nobles of the northern Russian city come to the royal review, where they are selected for the mysterious and frightening regiments of the German system for most of them. A nobleman from an ancient Russian family that had become Polish, entangled in his financial and family affairs, goes to command the defense of a fortress in the very east of the Polish-Lithuanian Commonwealth, completely unaware of what will meet him in the homeland of his ancestors. A former Cossack, who has long lived in slavery to a Crimean merchant, decides to pass himself off as the Tsar’s son, not even realizing how “at home” his idea will be to many people. The answer to many questions will be received during the assault on the fortress, the siege of which is led by a boyar from the Moscow family, the capital of whose appanage principality the besieged town was once - this is how the king decided to joke about his nobleman.