The homicide of a drug scientist placed in a cage forces Karp, who is on leave, back to work and Nurmi to work. The incisions in the back of the body lead to a complex murder mystery. Carp's daughter Henna encounters the miserable daily life of a criminal released from prison.

Remains of bodies are found in the sewer, which Carp tries to associate with the murder mystery he is investigating. Laura goes to the hospital and Nurmi starts tracking down the missing Leo boy. Henna is under pressure from both criminals and police.