Juvenile court magistrate Miss Thorpe is asked to offer advice to Lyla Lawrence, a fifteen-year-old girl who has run away from home. Miss Thorpe decides to tell her the cautionary tale of Gwen Rawlings, a girl who started down exactly the same path...
One day, Gwen's pawnbroker boss Mr Pottinger caught her apparently stealing a brooch from his safe (she was returning it after borrowing it to wear at a dance), and, after she spurned his opportunistic advances, he sacked her. She returned home to be beaten by her father. The next day, she packed her things and left.
She found a room in a boarding-house, sharing the top floor with the sharp-suited Jimmy Rosso. He introduced her to Max, proprietor of the Blue Angel nightclub, who hired her as a hat-check girl. She also met band members Art Moody and Red Farrell, the latter taking a paternal interest in her well-being. Jimmy made a pass at her after work, and was rebuffed.
Gwen's mother came to see her, pleading with her to return home. Gwen told her there was no sense in them both being persecuted. Red told Gwen that she was a born sybarite, too fond of the finer things in life. Jimmy watched their seemingly intimate encounter from a distance, and burst into Gwen's room later that evening.
Max, spotting Gwen's black eye, tricked Jimmy into confessing and sacked him. At the boarding-house, a conciliatory Jimmy asked Gwen to do him a favour by pawning his mother's jewellery - a pretty girl like her would get more money.
Max was attacked by a razor gang outside the club. Gwen told Red that she was terrified of going back to Jimmy, and he offered her a bed for the night at his place. Max hired a local hoodlum, Billy, to beat Jimmy up. At Red's place, Gwen discovered that he was married but separated. She hoped she could stay longer, but Red insisted that she leave the next day.
The police told Gwen that her former landlady Mrs Chalk had reported some jewellery missing and that a girl fitting Gwen's description had pawned it. She was arrested and tried at juvenile court. There, both Jimmy and Red gave evidence, but the court believed Jimmy's account, Miss Thorpe suspicious of Red's motives in taking a sixteen-year-old girl home. Mindful of Gwen's troubled family history, Miss Thorpe decided not to send her home but instead sentenced her to three years in an approved school.
There, Gwen fell in with Roberta, the school's most notorious trouble-maker, who taught her how to play the system. Both Red and her mother wrote numerous letters, but only the latter's were delivered. Gwen and Roberta bullied a younger girl, Agnes, into getting them cigarettes, but she reported them to Matron. A fight broke out in the food hall, providing Gwen with cover for an escape.
Gwen returned to the Blue Angel, then to the Silver Slipper club in Brighton, Max's new establishment. He was reluctant to have anything to do with her, but agreed to put her up after seeing her desperation. She quickly fell in with two regulars, Danny Martin and Fruity Lee, growing particularly close to Danny. One evening, a drunken drive turned to tragedy when a policeman was knocked down and killed. Danny told everyone in the car to hush it up.
When Inspector Girton, another club regular, quizzed Danny about his car, Gwen decided to flee. Danny caught up with her after she boarded the train, beat her up and stole her suitcase. Two American soldiers, Mickey and Al, found and helped her. All three effectively AWOL, they teamed up to rob people in London.
When their exploits became notorious, they resolved to go to Manchester, and flagged down a car with the intention of stealing it. The driver was Red. To Gwen's horror, Mickey and Al dragged him out of the car and, when they realised Gwen knew him (and vice versa), shot him dead. The car was trapped outside the gates of Hyde Park. Gwen was arrested and is now serving a fifteen-year sentence...
A chastened Lyla thanks Miss Thorpe and decides to return home after all.
