Autumn 1943. Three British agents working behind enemy lines are rounded up and shot. Who will be chosen to take their place?

The agents of the Outfit - at home and in Nazi-occupied France - have to cope with a series of crises. While Colin faces a breakdown and Vivien digs painfully into her past, Liz contemplates the wreckage of her private life and Emily must resolve an appalling personal dilemma.

Tensions in the circuit mount as Liz asserts her authority as the new leader. Gordon resents being bossed around by a woman. Vivien's mysterious behaviour arouses suspicion. And when disaster strikes, the team are forced to ask themselves: is there are traitor in their midst?

In the aftermath of the disastrous raid on the radio station the agents of Area 7 are faced with danger on all sides. How can they get treatment for the badly injured Gordon? Is there a traitor within their ranks? And what will happen when Emily disobeys orders for the first time.

With Emily on the run, Gordon invalided out, and Vivien increasingly obssessed with her secret search for her daughter, Liz struggles to prevent the disintegration of the circuit. She gets help from an unexpected source, but cannot stop the German noose from tightening around the beleaguered agents.

With Vivien and her daughter in German hands, Liz and the other agents of Area 7 are in grave danger, and they soon have to face a terrible dilemma. Which is more important? Their freedom or Vivien's life?