1918: As the Great War rages, Jessie Carson takes a leave of absence from the New York Public Library to work for the American Committee for Devastated France. This group of international women help rebuild destroyed French communities just miles from the front. Upon arrival, Jessie strives to establish something that the French have never seen --- children’s libraries. She turns ambulances into bookmobiles and trains the first French female librarians. Then she disappears. 1987: When NYPL librarian and aspiring writer Wendy Peterson stumbles across a passing reference to Jessie Carson in the archives, she becomes consumed with learning her fate. Eventually she discovers that they have more in common than their work at New York’s famed library, but she has no idea their paths will converge in surprising ways across time.

Paris, 1939: Young and ambitious Odile Souchet has it all: her handsome police officer beau and a dream job at the American Library in Paris. When the Nazis march into Paris, Odile stands to lose everything she holds dear, including her beloved library. Together with her fellow librarians, Odile joins the Resistance with the best weapons she has: books. But when the war finally ends, instead of freedom, Odile tastes the bitter sting of unspeakable betrayal. Montana, 1983: Lily is a lonely teenager looking for adventure in small-town Montana. Her interest is piqued by her solitary, elderly neighbor. As Lily uncovers more about her neighbor’s mysterious past, she finds that they share a love of language, the same longings and the same intense jealousy, never suspecting that a dark secret from the past connects them.