1942: With the war's outcome hanging in the balance, President Roosevelt sends an unlikely new taskforce on a unique mission. They are librarians and microfilm specialists trained in espionage, working with a special branch of the Office of Strategic Services and deployed to neutral cities throughout Europe. By acquiring and scouring Axis newspapers, books, technical manuals, and periodicals, the librarians can gather information about troop location, weaponry, and military plans.

Maria Alves, a microfilm expert working at the New York Public Library, is dispatched to Lisbon, where she meticulously photographs publications and sends the film to London to be analyzed. Working in tandem with Tiago Soares, a Portuguese bookstore owner on a precarious mission of his own, Maria acquires vital information, including a directory of arms factories in Germany.

But as she and Tiago grow closer, any future together is jeopardized when Maria's superiors ask her to pose as a double agent, feeding misinformation to Lars Steiger, a wealthy Swiss banker and Nazi sympathizer who launders Hitler's gold. Gaining Lars's trust will bring Maria into the very heart of the Fuhrer's inner circle. And it will provide her with a chance to help steer the course of war, if she is willing to take risks as great as the possible rewards . . .