A setting in World War II London, a shadowy spy agency, a curious lockpicker, an entertaining love triangle…need I go on? Ellie McDonnell, our heroine and aforementioned lockpicker, gets caught breaking into a safe, but instead of being arrested, she's offered a deal to work for (the handsome) Major Ramsey, to help intercept a treasonous message that's on its way to the Germans. But nothing goes to plan, and Ellie and Major Ramsey, along with a motley crew of small-time criminals, must undergo a series of dangerous operations.