Major Firsova becomes head of the department and investigates the death of his predecessor. This case leads her to a criminal network within law enforcement agencies. Somewhere nearby, a "mole" and a mysterious killer are operating, carrying out a sweep on orders from above. The further away, the fewer colleagues Firsova can trust remain. She will have to put together a puzzle of various details: contract killings, the loss of important evidence, the race for compromising evidence, a mysterious organized criminal group and a simply monstrous corruption conspiracy.