England, 1942: Liz Grainger lives a privileged life in Dover with her five-year-old daughter; Matty Fireman works in a London factory. Both are recruited as secret agents by charismatic Colonel James 'Cad' Cadogan.

Liz and Matty prepare for duty, and Liz bids a painful goodbye to her daughter. Under cover of night, the new agents fly to France.

Resistance leader Kit Vanston is shocked that the new arrivals are women. As German forces close in, wireless operator Matty sends her first transmission.

Matty narrowly escapes detection. Meanwhile, Liz learns that her childhood friend Claudine has been forced to billet German Colonel Krieger and his officers in her chateau.

Liz makes plans to return to London with vital information for Cad. Trapped between the Resistance and the Germans, Claudine faces a ghastly choice: become a double agent or be handed over to the Gestapo.

Liz's husband wants to know the truth about her wartime activities. When she comes clean, he's outraged. Back in France, Kit warns Matty to be more careful, and Claudine provides useful information to the Germans

Matty has been captured and Imprisoned, endangering the entire operation and the safety of its agents. Cad must send Liz to learn what is happening in France.

Matty's interrogation becomes increasingly brutal. Liz learns the awful truth about who betrayed her friend and mounts a dramatic rescue effort with Kit. Can they reach Matty in time?