The play revolves around the life of a young girl, Bessie, who works in a shirt factory in London's East End. The story takes a dramatic turn when Bessie, wearing a white pinafore, is mistakenly identified as a lady and becomes embroiled in a series of events that challenge her values and morals. As Bessie navigates her new surroundings, she encounters various characters who represent different aspects of society, including the aristocracy, the middle class, and the working class.