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 discovered 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, and through him learns much about the occupying forces. Kirsteen helps the local Resistance in attempting to sabotage the railway lines outside Paris but she is once again captured by the Germans and is tortured. Can she again escape, finally locate the missing British spy, and get him back to England?