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. Upon arrival, Jessie strives to establish children's libraries. She turns ambulances into bookmobiles and trains the first French female librarians. Then she disappears. 1987. When NYPL librarian Wendy Peterson stumbles across a passing reference to Jessie Carson in the archives, she becomes consumed with learning her fate. In her research, she discovers that she and the elusive librarian have more in common than their work at New York's famed library, and their paths will converge in surprising ways.