East London, 1940. Prue Carmichael never dreamed that she'd end up working at a railway yard. But when her reverend father is called up to Stepney, her family is uprooted from their country home for a new life in the turbulent city. Determined to help with the war effort, Prue signs up for work and soon becomes intrigued by handsome train engineer Jack Quinn. But as the spark between them grows apparent, so does his troubled past - a past that Prue's mother would certainly not approve of. In between cleaning train carriages and helping to shelter Jewish refugees, Prue manages to stay busy. But she has more than one admirer, and when Jack is recruited into Churchill's secret army, a very different suitor begins to pursue her. As air raid sirens sound overhead, Prue faces her own battle - the fight between her head and her heart...