On a whim, Juno Lambert buys a 1931 Underwood typewriter that once belonged to celebrated journalist Cordelia Capel. Within its case she discovers an unfinished novel, igniting a transatlantic journey to fill the gaps in the story of Cordelia and the family secret that lies concealed in its pages. Going back to 1936, Jane Thynne also tells the tale of how Cordelia begins a new life in Paris, even as her socialite sister Irene marries a German industrialist with Nazi sympathies, a decision that may permanently separate the sisters amid the turmoil of love, espionage, and war.