Trama

In Moscow, Russia, Viktor Chagarin (Sergei Kolesnikov), a high-ranking but corrupt Russian official, plans on incriminating political prisoner, former billionaire and government whistle-blower Yuri Komarov (Sebastian Koch) without a fair trial when Komarov refuses to hand over a secret file believed to have convicting evidence against Chagarin. In a separate incident, Jack McClane (Jai Courtney) is arrested as a result of an assassination but agrees to testify against Komarov for a shorter sentence.

John McClane (Bruce Willis), who has not been in touch with his son for years, learns of Jack's situation and travels to Russia to help. When McClane arrives and approaches the courthouse that holds Jack and Komarov on trial, an explosion orchestrated by Chagarin and his henchmen occurs in the courthouse, and Jack breaks free with Komarov. Seeing his son, McClane confronts him, but their dispute is cut short when apparently Chagarin's henchmen, led by Alik (Radivoje Bukvic), chase them on the streets of Moscow. Jack leaves John behind & takes Komarov with him. McClane, Jack, and Komarov escape, when John (following in a stolen SUV), rams Alik's vehicle & causes it to topple over. Jack then decides to come back & pickup John.

Jack & Komarov were supposed to be extracted by the CIA, but they are directed to a safe house when Jack misses the extraction window on account of delays due to dealing with John. Jack was not at all happy to see John as father and son haven't spoken in years.

Hiding in a safe house, McClane finds out that Jack has been a CIA officer in an undercover operation for the past three years. Collins (Cole Hauser), Jack's partner, demands the file's location from Komarov so that the CIA can bring Chagarin down. Komarov agrees to handover the file to Collins in exchange of his & his daughter's safe passage from Russia. He says that the file is in a vault, but the key is in a hotel is Moscow.

Collins is soon shot by Chagarin's men and dies, as McClane, Jack, and Komarov survive subsequent heavy gunfire and escape again. The trio then make their way to a hotel in the city to find the key to a vault containing the file. There, they meet Komarov's daughter, Irina (Yuliya Snigir), whom they earlier planned on joining with, but McClane grows suspicious of her, which is proven correct when Alik and his men crash in and tie McClane and Jack up, while Komarov is taken as a hostage, and Irina confesses to snitching on them for the "millions of dollars" to be gained. Jack breaks free of his ties, and the two succeed in killing most of the men. Alik and the rest of the henchmen come back on a Mil Mi-24 and try to kill them, but the two manage to escape. Meanwhile Irina takes Komarov hostage on a Mil Mi-24 copter & leaves the hotel.

Alik informs Chagarin that Komarov & Irina are taking him to the location of the file. Chagarin instructs Alik to kill Irina and Komarov when he has the file in his possession. Jack tells John that Chagarin & Komarov were partners in the Chernobyl nuclear plant. They used to siphon off weapons grade uranium from the plant for black market sales. Chagarin got greedy & that caused the meltdown. Komarov & Chagarin had a bad breakup. So, Chagarin threw Komarov in jail, but Komarov kept a file that would implicate Chagarin in the Chernobyl disaster.

That night, Jack & John steal a car full of firearms and drive to Chernobyl, Ukraine, the location of the vault that houses the file. When they arrive, they find that Komarov, Irina, and Alik have already arrived, but what they don't know is that on their way there, it was revealed that there was never a file in existence, and that the drawer with the file inside was actually the secret passage to a vault containing a large amount of weapons-grade uranium. Komarov kills Alik and calls Chagarin to tell him that he and Irina had manipulated the entire sequence of events since the beginning in an attempt to obtain the uranium and get revenge on Chagarin. Chagarin is then killed by a subordinate of Komarov.

At this point, McClane and Jack enter the vault, discover Komarov's true plot, and capture him. Irina, with another henchman, comes to her father's aid, but before they can escape, Jack goes after Komarov, while McClane goes after Irina, who is escaping on a Mil Mi-26 helicopter. Irina tries to protect her father by firing the helicopter's cannons at Jack, but McClane is able to bring the helicopter out of balance by driving a truck in its hangar section, still shackled by a chain, out of the open rear ramp of the helicopter. Komarov remarks that Jack will get to watch his father die, which enrages Jack to hurl him off the rooftop into the path of the spinning helicopter's rotors, killing him. McClane is thrown off the helicopter and reunites with Jack on the building. Wanting to avenge her father, Irina rams the helicopter into the building in a suicide attack, but both father and son survive by leaping off the building and into a large pool of water as the helicopter crashes and explodes, killing Irina.

Having mended their relationship, McClane and Jack return to New York, reuniting with Lucy (Mary Elizabeth Winstead), McClane's oldest child and Jack's sister.