For librarian Joyce Haddington, the pages of her favourite novels have always felt more compelling than her own life. But when war breaks out on her doorstep and a call for help rings out across the libraries of London, she knows she must act.

Taking matters into her own hands, Joyce invites a young Jewish girl to stay with her, and goes underground to begin her plans of resistance. Soon, emboldened by her friends in the Secret Society of Librarians, she pioneers a mobile library scheme to share the power of books in the darkest days of the war.

But Joyce's library cannot protect everyone. Far away in Lodz, Poland, her best friend Dorotha has fallen out of touch. Nobody can reach her - and Joyce is beginning to fear the worst . . .

Based on astonishing real events, this moving page-turner brings to life the remarkable untold story of two women during the war, and reinforces the power of knowledge and books in times of darkness.