Sam Giancana is a ruthless mob boss from Chicago. During a trip to Las Vegas, he sees a performance by the McGuire Sisters, a popular singing group with a pure image. Sam is attracted to Phyllis and begins aggressively courting her. The two enter into an epic romance, but it brings unwanted attention and tarnishes Phyllis's reputation. For Sam, however, the consequences are far more drastic, landing him in trouble with the law and his fellow mobsters.