Whip-smart librarian Peggy Sparks is determined to make sure that her brother Joe returns from the frontline to their London home, which they share with their beloved mother and grandmother. So when she is offered a once-in-a-lifetime job at the heart of the war effort, Peggy jumps at the prospect of making a real contribution to her country. But when she finds herself working under the fanciful socialite Lady Marigold Cecily, Peggy discovers that those around her are more keen on dancing at the CafeĢ de Paris than on ending the war.