1940: Austrian refugee Karl Lang has lost everything—his country, his home, and his family. All that is left to him is a burning ambition to see the Nazis defeated. Desperate for work and a way to help the war effort, he finds the one place that will take a refugee like him: a supply steamer traversing a deadly path past enemy U-boats.

Since their first meeting, Millie Stevens has felt an undeniable connection to Karl. As the war rages, she shares his determination to oppose the Nazis and finds work at the British codebreaking center at Bletchley Park. There she uses all her intellect and determination to break German codes and read U-boat transmissions—or risk losing the man she loves.

Rolf Denhart will do anything to defend the Fatherland, including long patrols in a cramped U-boat. But rumors from Germany leave him uneasy, forcing a choice between loyalty to his homeland, the safety of his family, and his peace of conscience.

In the midst of war, three lives are woven together to create an epic tapestry of love and loss, joy and pain, sacrifice and courage.