After their mother's death, Katerina and her younger sister Sonya are offered help by their aunt, Svetlana. She takes Sonya from Moldova, where the girls grew up, to live with her in Moscow. It is assumed that Katerina will soon move to Russia as well and take her sister with her. However, Svetlana secretly takes guardianship of Sonya and announces that the girl will now live with her permanently. Katya urgently comes to Moscow to help her sister, who is finding it increasingly difficult to get along with the domineering Svetlana. To have any chance of challenging her aunt's guardianship, she enters into a фиктивный marriage with Stepan — this way, she obtains a residence permit and the prospect of obtaining Russian citizenship.