St. Petersburg, 1871. Arseny Yablochkov, an official of the police investigations unit, is investigating the disappearance of the young Kapa Gnevysheva and the murder of her brother Kostik. The search leads him to a dacha cottage in one of the suburbs, where he finds the bloodied handkerchief of the missing girl. However, he can’t figure out what happened: the detective is knocked out by a blow to the head, and the cottage is set on fire…