Antonia Forrester, an English nurse, is nearly killed while trying to save soldiers fleeing at Dunkirk. Embittered, she returns to occupied Brussels as a British spy to foment resistance to the Nazis. She works with urban partisans who sabotage deportation efforts and execute collaborators, before résistante leader Sandrine Toussaint accepts her into the Comet Line, an operation to rescue downed Allied pilots. After capture and then escape from a deportation train headed for Auschwitz, the women join the Maquis fighting in the Ardenne Forests. Passion is the glowing ember that warms them amidst the winter carnage until London radio transmits the news they've waited for. Huddled in the darkness, they hear the coded message, "the long sobs of the violins" signaling that the Allied Invasion is about to begin.