Irena is arrested. Her stay there is a shock, and her fellow prisoners seem hostile. Karolina, convinced of her mother's innocence, starts her own investigation. Meanwhile, Jagoda gives Karolina and Michał another clue in the case murders in the den. Karolina follows her father's recent affairs and makes a surprising discovery in her parents' house.

Irena manages to gain the respect of the prisoners in her cell. Karolina and Michał trace the connections between the people involved in the murder in the den and discover who withdrew the money from the victim's account. At the same time, Karolina tries to decipher the data from the notebook father and reveals to Michał that he is conducting a private investigation. Together they reach an abandoned premises and find traces of a dangerous practice.

The prisoners from Irena's cell plan to escape, but not everything goes according to plan and a tragedy occurs. Karolina cannot come to terms with what she learned about her father. At the same time, he realizes that he could not act alone. During the Holidays Michał and his colleagues are trying to solve the murder case in the den, but Karolina still has doubts about the guilt of the arrested person. Michał decides to check her suspicions one last time