In 2000, boxes containing top-secret files were found in a garden shed in Cornwall. They detailed the lives and code names of Britain's first female agents sent to the front line during the war. The British spymistress, Vera Atkins, had committed treason by keeping the papers, but she had a reason for doing so. During the war, Prime Minister Churchill desperately needed foreign agents, and though women were not allowed to fight on the front line, they could be sent behind enemy lines as spies. Vera was put in charge of the female spies, and when many of them went missing during the war, never to return, she was determined to find out their fate – in defiance of the British authorities. Vera's files were kept sealed until after she died, but the story of the female spies and the spymistress who led them, which has remained secret for over 50 years, can now be revealed.