When the police raid a gambling and prostitution house, its owner, "Lucky" Wilder, is found dead, and Mae Miller is accused of his murder. While defending herself in court, Mae tells the district attorney how she was naïvely drawn by her friend, Molly Murdock, into a racket that "gambles with souls." Mae's story begins with her living frugally, but happily, with her husband John, who is busy with medical research. After Mae wins at bridge, Molly takes her to Wilder's club, where she wins five hundred dollars her first evening. Soon Mae becomes addicted to gambling and expensive living and is $10,000 in debt to Wilder with nowhere to turn. Molly, meanwhile, has been running a sex exchange through Wilder's club, luring thrill-seeking girls into gambling, then forcing them to entertain Wilder's male clientele when they can no longer pay their debts. After Wilder threatens to expose Mae to her husband, she dines with "Million Dollar" Taylor, who promises to lend her $1,000 and seduces her. Then, while John is in Chicago, finally receiving recognition for his surgical techniques, Mae runs away and becomes one of Wilder's girls. When John returns, he and Mae's younger sister Carolyn search for Mae in vain until, in a seedy club where Molly and Lucky frequently dine, John hears Mae's laugh following a shooting incident and finds her with the criminal. While John is away from the table, Lucky befriends Carolyn and soon she is repeating her sister's path to degradation. Later Mae discovers Carolyn has had an abortion and visits her in the hospital, where Carolyn dies. At the end of the district attorney's inquisition, Mae admits to killing Lucky to avenge her sister's death, and John begs the district attorney to give him back his wife.