In the heart of Moscow, Russia, corrupt politician Viktor Chagarin (played by Sergei Kolesnikov) devises a ruthless plan to frame political prisoner Yuri Komarov (portrayed by Sebastian Koch), a former billionaire-turned-whistleblower. This nefarious scheme arises when Komarov declines to surrender a secret file containing incriminating evidence against Chagarin. Meanwhile, Jack McClane (played by Jai Courtney) finds himself embroiled in a separate incident, leading to his arrest for an assassination. However, he offers to testify against Komarov in exchange for a reduced sentence.
Enter John McClane (Bruce Willis), who, despite years of estrangement, rushes to Russia upon learning of his son's predicament. As he approaches the courthouse where Jack and Komarov are being tried, chaos erupts when Chagarin's henchmen orchestrate a violent explosion, allowing Jack and Komarov to escape. A tense reunion occurs, abruptly interrupted by the pursuit of Chagarin's goons, led by Alik (Radivoje Bukvic). Despite the turmoil, John makes a daring move using a stolen SUV to aid their getaway. After a tense moment, Jack decides to backtrack and ensure his father’s safety.
Initially meant to be extracted by the CIA, Jack and Komarov find themselves diverted to a safe house after a delay caused by John’s interference. In this hideout, John learns that Jack has been operating undercover for the CIA. As Collins (played by Cole Hauser), Jack's partner, demands the location of the file, Komarov suggests they retrieve it in exchange for safe passage for himself and his daughter Irina (Yuliya Snigir) out of Russia. The file, located in a vault, requires a key that can be found at a local hotel.
Tragedy strikes as Collins falls victim to Chagarin's men, but McClane, Jack, and Komarov manage to escape amidst gunfire. Determined, they head to the hotel to find the key. There, they unexpectedly encounter Irina, but John's skepticism is validated when Irina betrays them, revealing her ulterior motives for money. In a thrilling turn, Jack frees himself, leading a bloody confrontation where they manage to fend off the attackers. Irina, however, successfully abducts Komarov and escapes via helicopter.
As tensions rise, Irina's treachery unfolds, unveiling a deeper conspiracy tied to the Chernobyl nuclear plant, where Chagarin and Komarov originally collaborated to siphon weapons-grade uranium, resulting in disaster. Jack and John, aware of Chagarin's dark past, set off to Chernobyl, eager to uncover the truth. Upon arrival, they discover that Komarov has cleverly orchestrated events to seize the uranium for revenge.
The stakes escalate dramatically when McClane and Jack confront Komarov and Irina in a thrilling climax. With danger closing in from every angle, they engage in an intense showdown. Jack's fury peaks when he faces Komarov, who revels in the chaos he’s created. In a final confrontation, Jack dispatches Komarov, but Irina's desire for vengeance leads her to a deadly confrontation with the duo. As the helicopter crashes in a fiery explosion, John and Jack's narrow escape signifies the resolution of their strained relationship.
Ultimately, father and son return to New York, where they rekindle their bonds with Jack's sister Lucy (played by Mary Elizabeth Winstead), bringing a bittersweet closure to their harrowing ordeal.
