The game is based in the American city of Chicago in the 1930s; an era heavily associated with gangsters. The RPG style game allows players to choose to be the mafia, headed by Don Carmine Falcone, or a special unit of the police, headed by Edward Nash.
- Mafia: If you choose to play as Mafia, you'll play as Jack Beretto, member of the local Mafia and right-hand man of Don Carmine Falcone. Playing as Mafia, your goal is to destroy all of your enemies and take over Chicago. The powerful Irish organized crime leader, Hank O'Neil is head of Chicago and there's this mysterious character "Baron" who is apparently stealing money from Don Falcone. When it's revealed that O'Neil is not the Baron, new character will get into plot: District Attorney Dan D. Dougherty. But, it will be also revealed that Dougherty isn't the Baron after all. To find out the Baron, play the next chapter.
- Police: If you choose to play as Police, you'll play as Edward Nash, the FBI agent. The FBI head will give you missions. Now the antagonist is Don Falcone, who is already the king of Chicago. You'll have to slowly take over Falcone's territories as you proceed to ruin his empire. The traitor Beretto will help you a little, but he is also an enemy. At the end of this chapter you will find out who is hiding under the Baron name. Familiar character, that's for sure.
- Henchmen: These are people that help your main protagonist (Jack Beretto or Edward Nash). They are also playable characters and can use for different tasks (for example, a gangster or officer with high shooting skill can be sent to kill by shooting.). Game won't be over if a henchman dies.
- Don Carmine Falcone: The brutal Mafia boss from New York, shows up in Chicago. If you play for his Mafia empire, you'll have to beat bunch of enemies on your way to top. Notice, that his name and story are a parody on Al Capone
- Jack Beretto: Right-hand man of Don Falcone, Jack is the protagonist of the first chapter. In second chapter he will help you a little with infos against Falcone, but you will still have to put him behind bars. Responsible for killing Hank O'Neil and Dan D. Dougherty, two antagonists.
- Edward Nash: Protagonist of second chapter, FBI agent. Notice that his name and story are similar to that of Eliott Ness.
- FBI Head: Man giving you orders in second chapter.
- District Attorney Dan D. Dougherty: Man who was supposed to be Baron, but it is revealed he's not. Kidnapped and interrogated by Don Falcone, and later killed on his orders. If you play as police, your first mission will be to investigate the death of Dougherty.
- Hank O'Neil: Irish mobster, ruler of Chicago before Don Falcone and second antagonist in first chapter (the other being District Attorney Dan D. Dougherty). Killed on Don Falcone's orders, last mission in first chapter.