Winston Churchill has a "Secret Circle" of specially trained spies who are answerable only to him. Kirsteen Craig, a young nurse who shows her bravery during a London bombing raid, is recruited by Churchill and trained to go into occupied France to try to locate a top operative who has gone missing. After blending in with the French Resistance, Kirsteen manages to make a number of important contacts but is eventually picked up by the Gestapo and imprisoned. However, she manages to escape. A Gestapo officer befriends her and seems to become attracted to her. She finds herself similarly attracted to him. Through him, she learns much about the occupying forces. Kirsteen helps the local Resistance in attempting to sabotage the railway lines outside Paris. She is once again captured by the Germans and is tortured before escaping. She eventually locates the missing British spy and is instrumental in rescuing him and eventually getting him out of France and back to England.