The brutal murder of a young girl launches an extended police investigation. Detective Sarah Lund is supposed to leave for a new life in Sweden, but can't bring herself to leave the case behind. The girl's parents and friends struggle to cope with their loss. Troels Hartmann is campaigning to be mayor of Copenhagen, but struggles when links are revealed between city hall and the murder. Over a time span of twenty days, suspect upon suspect is sought out as violence and political pressures cast their shadows over the hunt for the killer.