Rita Sorokina, a law student who is diligently preparing for her state exams, learns that her mother has died in a fire at a country house. The investigation establishes that she was there with her lover and that the fire was caused by an unextinguished cigarette. The incident is considered an accident, but Rita gets her law degree and decides to investigate on her own. Rita's father and her boyfriend Artem are strongly opposed to this, and Artem keeps her busy with work so that she has no time to investigate the circumstances of her mother's death.