May Lloyd's father calls her his homing pigeon because of her uncanny knack of navigating her way around the streets of South London—even in pitch darkness. It is a gift that will save her life when the Blitz destroys nearly everything that she holds dear. With her home in ruins, May joins the ATS—the women's branch of the British Army—and becomes a gunner girl, operating Ack Ack guns against the Luftwaffe. Meanwhile, her sister Peggy makes a daring bid to escape a stifling marriage and find love and freedom amid the heady chaos of war.