On day one of the experiment, the officers patrol the tense Klara district. Carin searches for a lost item but finds more than she bargained for.

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.