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 her family's ancestral home in London. She and Mat discover diaries and letters that reveal her grandmother and great-aunt were known as the "Waite sisters". 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.