Iconoclastic, take-no-prisoners cop John McClane, finds himself for the first time on foreign soil after traveling to Moscow to help his wayward son Jack - unaware that Jack is really a highly-trained CIA operative out to stop a nuclear weapons heist. With the Russian underworld in pursuit, and battling a countdown to war, the two McClanes discover that their opposing methods make them unstoppable heroes. John McClane travels to Russia to help out his seemingly wayward son, Jack, only to discover that Jack is a CIA operative working undercover, causing the father and son to team up against underworld forces.