Flame (Thure Lindhardt) and Citron (Mads Mikkelsen) are the code names for two Danish assassins hired by the Holger Danske resistance group to go after Danish informers and occupying Germans in 1944 Copenhagen. While Flame dreams of launching a counterattack on the Nazi forces, sensitive family man Citron is more concerned with the political workings of the group. When boss Aksel Winther (Peter Mygind) orders Flame to execute his girlfriend, a beautiful courier called Ketty (Stine Stengade), he finds himself questioning the order. Something doesn't feel right and all of a sudden the lines between fact and fiction become blurred. Nobody is sure who to trust or who is really working for whom. Realising they've only got each other to rely on, Flame and Citron now focus their efforts on locating Hoffmann (Christian Berkel), the much-hated chief of the Gestapo.