Pennsylvania, 1956. Frank Sheeran, a war veteran of Irish origin who works as a truck driver, accidentally meets mobster Russell Bufalino. Once Frank becomes his trusted man, Bufalino sends him to Chicago with the task of helping Jimmy Hoffa, a powerful union leader related to organized crime, with whom Frank will maintain a close friendship for nearly twenty years.

As the heat rises in a stuffy hotel room, a talking ice cube pitches the wonders of modern refrigeration to a strangely distracted man.

To take down South Boston's Irish Mafia, the police send in one of their own to infiltrate the underworld, not realizing the syndicate has done likewise. While an undercover cop curries favor with the mob kingpin, a career criminal rises through the police ranks. But both sides soon discover there's a mole among them.