 Chicago, 1930, during the Prohibition Era. Trading with alcohol was illegal amd the mafia is rules the city. Don Falcone entered the city and opresses the people. Edward Nash and his special police unit is sent to stop the crimes of the mob. A war between the two fraction breakes out, between rivaling gangs and between the FBI and the mob. You as the player can choose wether to fight on the side of the police or on the side of the mafia. Being in control of the mob, you attempt murders, kidnap people your main target is take control over the whole city. As the police you try to free the city quarter after quarter and you re accepting many different missions like investigations.