In the fourth episode, the investigation into the brutal murder of the Loshkarev family intensifies. As the team searches for motives and suspects, the plot focuses on:

: The youngest son, who was the only survivor of the attack, remains a critical but traumatized source of information.

: The episode delves deeper into Chayanov's reputation as a top investigator and the pressure he faces to solve the case despite the high-stakes environment of Soviet-era law enforcement.