Inspector Sarah Lund (Sofie Gråbøl) is about to quit her job and go to Sweden with her son to start a new life with her boyfriend. However, before leaving, she is forced to take over a difficult case with the new successor Inspector Jan Meyer (Søren Malling): the murder of the girl Nanna Birk Larsen. At this time, the mayoral election in Copenhagen is in a fierce state, and the young and promising candidate Troels Hartmann (Lars Mikkelsen) has a good chance of winning. However, his campaign team is inextricably linked to the murder of the girl. As the investigation deepens, Sarah's personal life is also changed by the case, but the truth has not yet surfaced...