The Boss is essentially a card game (with a small game board for keeping scores) of deduction, bluffing, and a lot of backstabbing.
In the game, there is loot distributed across the US, in various cities, and with the play of each card players gain more information about the loot that may be theirs for the taking (or sanctions to avoid). Gang members (some pros, some amateurs) are sent to those cities. Whoever has the most gang members in a city grabs the loot or suffers the sanction. When going to Chicago, you have no choice but to split your takings with the boss himself: Al Capone. The further the game progresses, the higher the stakes are, especially in Chicago. As with any back-stabby game, be confident of your friendships first!