Twenty-six-year old Peggy Thornton is a middle-class girl living in the heart of working-class Islington. Although she loves her parents, Peggy has always felt her home life to be narrow and claustrophobic so, when women are urged to help on the home front after the outbreak of the Second World War, she starts training as a conductor on a London Transport bus. Her parents are both appalled; it's hardly a fitting position for the daughter of a local magistrate. It is not just Peggy's parents who make her life difficult. Many of the bus crew haven't adjusted to women from their own class working let alone the likes of Peggy. And her relationship with Leo, who is most definitely from the wrong part of town, serves to create further tensions. It is only when the real enemy strikes, and a bomb explodes in the path of a bus, that these petty differences are cast aside, but, for some, it's too late to say sorry.