New York mobster Benjamin Bugsy Siegel (Warren Beatty) leaves New York City to dip into the glamour of Hollywood, Calif., and to build up syndicate gambling rackets. Bowled over by actress Virginia Hill (Annette Bening), the dapper Siegel courts her, despite having a wife and children. Obsessed with creating a gambling haven, Siegel takes racketeering to the Nevada desert and helps develop Las Vegas, only to find himself in deep water over his reckless construction of the Flamingo Hotel.