In the 1920's, ambitious but small time thief Jack Diamond (Ray Danton) and his sickly brother Eddie Diamond (Warren Oates) move to New York City. Jack meets dance instructor Alice Shiffer (Karen Steele), lies to her to date her and to steal a necklace from a jewelry store. After being incarcerated for a time, he works with Alice at her dance school while on probation. He then gets hired as bodyguard of infamous Arnold Rothstein (Robert Lowery) who gives him the nickname Legs. His plan is to supplant Rothstein with the intention of stealing his bootleg, drugs and gambling businesses. After Arnold is murdered, Legs Diamond sells protection. When he travels to Europe with Alice on a vacation, he sees in the newspaper that the New York underworld has changed with the National Prohibition Act...Legs returns to America and confronts the syndicate, demanding a cut from their operations. He kicks Alice out of his life and turns to Monica (Elaine Stewart), who betrays him. Hit men enter his hotel room and shoot him dead. In the final scene, as his corpse is being removed on a stretcher, Alice says he was loved by many but that he loved nobody.