1944. While the Danish population hopes for a swift end to the war, freedom fighters Bent Faurschou-Hviid (23), a.k.a. Flame and Jorgen Haagen Schmith (33), a.k.a. Citron, secretly put their lives at stake fighting for the Holger Danske resistance group. The fearless and uncompromising Flame is a confirmed anti-fascist and dreams of the day when the group will assemble and openly launch an armed counterattack at the occupying power. The more sensitive family man, Citron, used to work primarily as a driver for Flame, but now finds himself becoming more deeply involved in the group's work. When their immediate superior, Aksel Winther, orders them into action against two German Abwehr officers, events start to get out of hand. Flame engages in conversation with the talented and intelligent Colonel Gilbert and for first time, Flame calls the soundness of the order he is about to execute into question... Something feels terribly wrong. Furthermore, when suspicion turns to his girlfriend, the beautiful and mysterious courier, Ketty, Flame begins to spot the outline of a different and mostly hidden agenda. Can Ketty be trusted? Can Winther? And who really works for whom? While their doubts gnaw at them, Flame and Citron come to feel that they are on shaky ground. Desperate, disillusioned and with a sense of having been betrayed by their superiors, they decide only to trust each other and concentrate their efforts on getting to the much hated and feared chief of the Gestapo, Hoffmann. The film is based on actual events and eyewitness accounts from some of the people who experienced Bent Faurschou-Hviid ("Flame") and Jorgen Haagen Schmith ("Citron") at very close range. Flame & Citron bases itself on a monumental amount of ground breaking research of actual historical events. Director Ole Christian Madsen and screenwriter Lars K. Anderson carried out this new research over the course of several years, including interviews with numerous survivors and eye witnesses, many of whom have since died.