As the Chicago Mafia attempts to murder witnesses who could incriminate them in court, Mark Kaminsky (Arnold Schwarzenegger), a former FBI agent, sets out to infiltrate the organization and root out the assassins -- including ruthless mob leader Luigi Patrovita (Sam Wanamaker). But there's more to this mission than justice: Patrovita killed the son of Kaminsky's old FBI friend, Harry Shannon (Darren McGavin), who wants revenge.