London, 1938. Bookseller Gertie Bingham is facing difficult times, having just lost her beloved husband, Harry, and with a lingering sadness at never having been able to have a child of her own. Struggling to face running the bookshop she and Harry opened together, Gertie is preparing to sell up and move away when she is asked if she would be willing to take in a young Jewish refugee from Germany. Gertie is unsure and when sullen teenager Hedy Fischer arrives, Gertie fears she has nothing left to give the troubled girl. But when the German bombers come and the lights go out over London, Gertie and Hedy realise that joining forces will make them stronger, and that books have the power to bring young and old together and unite a community in need in its darkest hour...