Liverpool, 1940. Journalist Ruth Holt is struggling in the terror of the Blitz when her young son is suddenly snatched away in broad daylight. Soon after, the kidnappers' demands arrive. They are working with the Nazis, and she has no choice but to cooperate, or the authorities will learn that she is harbouring secrets of her own. Ruth's job gives her access to critical information, and if she does not share it with Britain's enemies, her child will face the consequences. Desperate, she falsifies information, lying to everyone: her employers, her family and her lover. But as the demands increase, the knife edge she walks on grows increasingly thin. If she falls, she will never save her son.