Juliet Armstrong is a dissatisfied radio producer in a 1950s London that is recovering from the war as much as she is. During World War Two, Juliet was conscripted into service, transcribing conversations between an MI5 agent and a ring of suspected German sympathizers. The seemingly dull work quickly plunged Juliet into a treacherous world of code words and secret meetings where Juliet herself was sent into the field. These moments of intrigue and romance feel like a lifetime ago as Juliet trudges through her commute, her job and her new life. But as Juliet and the rest of London find ways to return to normal, her routine is upended by an encounter with a mysterious man from her past life. Haunted by the relationships and actions of her past and facing a very real threat in the present, Juliet cannot escape the repercussions of her work for the government. With no other choice, Juliet is quickly pulled back into the life of espionage she thought she'd left behind.