Inspired by the remarkable life of Dorothy Peto, the Metropolitan Police's first female superintendent.

In 1914, the idea of a female police officer is dismissed as absurd, but to a small group of determined women, not impossible.

With men departing to fight for king and country, women have new opportunities at home. Dorothy Peto and her fellow suffragettes propose forming the Women's Police Volunteers to assist police keep order. At first, the suggestion is derided, yet the force is stretched thin. As Dorothy and her friends train and organise to help refugees fleeing the war and guide terrorised Londoners to shelter during the Zeppelin raids, the 'ladies in blue' gain a grudging acceptance.

During one nightly bombing raid, Dorothy discovers the body of a beautiful, Belgian refugee in Seven Dials. Convinced the woman was murdered before the bombs fell, Dorothy's determined to investigate even though the battle-scarred Scotland Yard Inspector remains skeptical of her ideas and enthusiasm. As the list of suspects grows—a British aristocrat, a Belgian gangster and a wealthy German industrialist—Dorothy must outwit the killer, and even some within the WPV.