New York City cop John McClane (Bruce Willis) arrives in Moscow to track down his estranged son, Jack (Jai Courtney) . McClane thinks his son is a criminal, so it comes as a shock when he learns that Jack is actually working undercover to protect Komarov (Sebastian Koch), a Russian government whistleblower. With their own lives on the line, McClane and Jack must overcome their differences in order to get Komarov to safety and thwart a potentially disastrous crime in the Chernobyl region.