John McClane, a seasoned New York City cop, learns that his estranged son Jack, whom he believed to be a criminal, has been arrested in Moscow for assassination and is facing a lengthy prison sentence. Determined to help his son and hoping to reconnect, John heads to Russia. However, upon arriving, he quickly realizes that Jack is deeply involved in something far more complicated than a simple arrest. Jack is actually a CIA operative on an undercover mission to prevent a nuclear-weapons heist, complicating John's hopes for a simple father-son reconciliation.

As John stumbles upon Jack's operation, the two are forced to team up against formidable odds. They find themselves in the midst of a dangerous political conflict involving corrupt Russian officials and a key figure in the opposition with secrets capable of destabilizing the nation. The McClanes are drawn into a deadly game of cat and mouse within the chaotic backdrop of Moscow's treacherous underworld. Engaging in gunfights and car chases, father and son must put aside their differences and work together to thwart a criminal plot that threatens global security.