World War I. Frieda ran away from home because her bi-atch mom wants to marry her off to a man twice her age. She works at a high end department store and her salary is barely enough to feed her and keep a roof over her head, but she's happy. She's happy because she thinks she's free from her mother's judgment and control. She is living her own life and thinking for herself. Her friends are "charity girls", not quite prostitutes but girls who use their looks and womanly wiles to get material things.
Frieda isn't one of those girls though. She is a romantic who believes in true love, and that, turns to be her downfall. An encounter with a handsome soldier leads to her being imprisoned for immorality, having been infected with an STD. Along the way, she is subjected to a great many degradations but manages to keep herself upbeat and hopeful, and still fighting.
The book is actually based on true happening during WWI about many girls being imprisoned just for looking slutty or some other equally stupid reasons, in an over zealous fight agains immorality and venereal disease. The author paints a picture of that era very well and you can almost see it in you mind. The book is essentially a portrait of that period in time, of that peculiar bump in history.