The mysterious disappearance of seventeen-year-old Sonya Pankova and her thirteen-year-old admirer Vasya Afanasyev during a school trip to the museum forces investigators to start looking for a motive for what happened. Soon they manage to hot on the trail to find Afanasyev, who decided to stage his abduction and was caught together with his accomplice while transferring the ransom by his father.

In a rented apartment, single mother Elena Filimonova and her ten-year-old daughter Masha were killed and raped. The friend of the deceased, Ekaterina Stroeva, says that the Filimonovs lived poorly, and Elena constantly had to borrow money, and shortly before the tragedy, the apartment owner offered her to lower the rent in exchange for sex with him.