Al Capone has his first taste of the underworld in Brooklyn with Johnny Torrio; they reunite in Chicago and start bootlegging, earning the ire of local Irish gangsters.

"A Death in the Family" After the killing of "Big Jim" Colosimo, Capone and Torrio expand their criminal empire into bootlegging but are forced to make a truce with the Irish North Side gangster Dion O'Banion. When a new Chicago mayor is elected, Capone and Torrio are forced to move their headquarters to the working class suburb of Cicero. Torrio is forced to take a leave of absence in Italy, and Capone assumes temporary control of the Outfit with the help of his brothers Frank and Ralph. When Cicero holds its own mayoral election, however, Capone orders his brother ...

A betrayal destroys peace in Chicago. Torrio and Capone seek revenge against the Irish gangs. Meanwhile, the Beer Wars make Capone Chicago's top gangster.

Capone uses the St. Valentine's Day Massacre to assert his power over his enemies. Meanwhile, President Hoover takes notice; and dispatches Elliot Ness to take on Capone.

Al Capone outwits Eliot Ness, but Capone's criminal empire remains in jeopardy when the IRS plants an undercover agent in his gang.

With Capone in jail, Frank Nitti, Paul Ricca and Joe Accardo take over. Meanwhile, a Hollywood scandal presents Sam Giancana with a chance to prove himself.

Joe Accardo sets his sights on Las Vegas, but when Sam Giancana incurs the wrath of young attorney Robert F. Kennedy, The Outfit is threatened.

In the second-season finale, Joe Accardo and Sam Giancana have a falling out and the fate of the Outfit rests on the outcome. Meanwhile, Joe Accardo cleans up loose ends before retiring.