Uncovering a dark family secret sends one woman on the journey of a lifetime--through the history of Britain's WWII spy network and glamorous 1930s Paris--in an effort to understand her past, save her family, and shape her future.

Caroline Payne thinks it's just another day of work until she receives a call from Mat Hammond, an old college friend and historian. But pleasantries are cut short. Mat has uncovered a scandalous secret kept buried for decades: In World War II, Caroline's British great-aunt betrayed family and country to marry her German lover.

Determined to find answers and save her family's reputation, Caroline flies to the old family house in London. She and Mat discover diaries and letters that reveal her grandmother and great-aunt were known as the "Waite sisters." Popular and witty, they came of age during the interwar years, a time of peace and luxury filled with dances, jazz clubs, and romance. The buoyant tone of the correspondence soon yields to sadder revelations as the sisters grow apart and one leaves home to join the glittering fashion scene of Paris, despite rumblings of a coming world war.

Each letter brings more questions. Was Caroline's great-aunt actually a traitor and Nazi collaborator, or is there a more complex truth buried in the past? Together, Caroline and Mat uncover stories of spies and secrets, love and heartbreak, and the events of one fateful evening in 1941 that changed everything.

In this rich historical novel from award-winning author Katherine Reay, a young woman is tasked with writing the next chapter of her family's story. But Caroline must choose whether to embrace a love of her own and proceed with caution if the decades-old wounds of a family are to heal without tearing them even further apart.