The rich heiress Varvara and her sworn sister Margarita were best friends until their love for Dmitry Grivin made them rivals. And when Varvara married Dmitry, and Margarita became the wife of Varvara’s father, they became mortal enemies. A year after the wedding, Margarita’s husband dies under mysterious circumstances, and Varvara accuses her stepmother of murder. Margarita's last chance is the insightful and meticulous investigator Serdyukov.