Ness was the nemesis of Frank Nitti, a notorious gangster in the 1920s and 1930s. He was the leader of the Chicago Outfit, a criminal organization that was part of the larger American Mafia. NESS was an American Prohibition agent who was tasked with bringing down Nitti and his organization. He was successful in his mission and eventually brought down the entire Chicago Outfit. Nitti was eventually convicted and sentenced to prison, where he died in 1943. NESS and Nitti's rivalry is remembered as one of the most famous in American crime history.