Billie Challinor's mother dies during an air raid, but the child grows up confident that in her jazz musician father Chas she has the best dad in the world. Seeking refuge from the London Blitz by moving to Leeds, kindly landlady Liz Morris befriends them: the scarred, wisecracking man, who isn't afraid to overstep the mark if the cause is a good one, and his clever and resilient little girl. Billie needs every ounce of courage she possesses when her father joins the Army just before the D-Day landings and fails to return.

Though Liz is happy to raise the child as her own, Billie is claimed by her Uncle Cedric, an outwardly respectable and prosperous solicitor. But he is also a ruthless criminal mastermind who will stop at nothing to secure the fortune to which Billie is sole heiress. Confident of his superior strength and cunning, he foolishly overlooks the fact that she is her father's daughter: resourceful, quick-witted, and ready to seize any chance she can to escape his deadly clutches and return to her beloved Aunt Liz.