The film begins on Mother's Day, 1938 when 14-year-old Ziggy Brennan buys a gardenia for her mother. Ziggy's youthful exuberance disappears when she enters their apartment and finds her mother, Natalie drinking with a strange man. Natalie introduces Ziggy as her "sister" and quietly cautions Ziggy against calling her "mother." Later, dispensing some motherly-advice, Natalie tells Ziggy that if she learns all the tricks, she'll never have to work for a living. Ziggy goes right out and applies parts of this advice by stealing a valuable lapel pin from a fellow high-school student, and is promptly expelled from school. About five years later, Ziggy has made progress and meets Denny Reagan who persuades her to go into his racket. Ziggy's role is to telephone people who are planning to move and make arrangements to provide a truck to move the furniture. The departing truck is the last that the owners see of their furniture as it is taken to a warehouse and sold by Denny and his gang. Hanging out in a nightclub one evening, circa 1943, the still-underage Ziggy flirts with a young naval officer from Minnesota, Mart Neilson, who promptly falls in love with Ziggy and proposes marriage. Ziggy, to ensure that Mart knows her background, introduces him to Natalie (at her worst), but Mart doesn't change his mind and still insists on the marriage. Shortly after the wedding ceremony, Mart is shipped out to war-duty and is killed in action. Ziggy learns that she is expecting a baby, while the law catches up to Denny and ships him out to prison. Ziggy is still living with her mother but Natalie, horrified at the prospect of being a grandmother, kicks her out and Ziggy moves into Mrs. Merryman's boarding-house. Ziggy has the baby and some time passes, circa 1944-45, and Ziggy---still making her nightclub rounds---runs into the just-paroled Denny. This Denny is a new-and-thoughtful version, and he does not approve of Ziggy leaving her baby with a sitter while she makes her rounds. Denny shows great interest in the baby and sees more and more of Ziggy. Returing from a date, Ziggy finds the baby's crib vacant. In her absence the baby-sitter had gone out to her boyfriend's car for some heavy necking and, in her absence, the baby had almost choked to death before being discovered by Mrs. Merryman, who promptly called the police. At the trial, the baby-sitter denies responsibility (negligence-of-duty)and Ziggy loses custody of her baby. The new-and-thoughtful Denny will have nothing to do with Ziggy, even though his mother, knowing that Denny and Ziggy really love each other tries to bring them together. But...Ziggy has disappeared. Ziggy, having moved to another boardinghouse, drops by a church and finds an abandoned baby. Later, Denny finds her, while she and the baby are sunning in a park, and he is greatly impressed with new-and-thoughtful mother-instincts, and he is convinced that she has become a perfect mother. With Denny's help, Ziggy appeals her case in order to regain custody of her own child and, when the judge learns that she has been caring for an abandoned baby, he is much impressed and returns her own infant to her.