Carin receives a mysterious letter and decides to investigate a case outside her jurisdiction, while Ingrid challenges troubling conduct at the station.

An abrupt exit casts doubt on the experiment's future. A surprise guest arrives for Carin, and a powerful external force pulls strings behind the scenes.

The women start finding their feet, with Siv earning respect for an arrest and Carin determined to uncover the truth, but Ingrid's conscience irks her.