The film starts with news coverage on Yuri Komorov (Sebastian Koch), a man imprisoned for political reasons. He is visited in his cell by another man named Viktor Chagarin (Sergei Kolesnikov), asking him about a file, but Komorov won't say a thing. Chagarin later gets a couple of people together to get what Komorov has. Meanwhile, in a club in Moscow, Jack McClane (Jai Courtney) walks up to a man named Anton (Roman Luknar) and tells him "Komorov says hello...and goodbye" before shooting him. Jack then gets tackled to the ground.
We catch up with John McClane (Bruce Willis) at a shooting range when he is met by his friend Murphy (Amaury Nolasco). He tells him Jack is imprisoned in Moscow, and John mentions not having seen Jack in a long time, especially since their last meeting was unpleasant. He goes to get him out and is taken to the airport by his daughter Lucy (Mary Elizabeth Winstead). As soon as he gets to Russia, he attempts to brush up on his language, but he's not good. The driver of a cab he enters warms up to him when he realizes he's a New Yorker and he starts singing a Sinatra song. With the traffic being heavy, the driver lets John walk out and not pay anything.
John ends up walking far enough to see Jack being taken to a courthouse with Komorov. Both of them are almost put on trial when a man named Alik (Radivoje Bukvic) blows up a bunch of cars and destroys part of the courthouse, allowing Jack and Komorov to escape. John runs into the car that Jack takes, and Jack is none too happy to see him. Alik and his goons try and grab Komorov but Jack escapes, forcing John to hijack a truck and chase after them. Jack patches through to his CIA colleagues and is told to take Komorov to a man named Collins. After a lengthy chase, the McClanes outrun Alik and his henchman. John wrecks his truck, but Jack lets him climb into their vehicle.
The McClanes and Komorov reach a safe house and meet with Collins (Cole Hauser). He asks Komorov for a file that would allow him to get out of Russia, but Komorov says it's locked somewhere, and he knows where the key is. To ensure the file's security, Komorov asks if he can bring his daughter Irina with him. After making a phone call, a bunch of men come in and start shooting, killing Collins. The McClanes narrowly escape with Komorov again.
Before going to find the key, John and Jack argue. When Jack isn't around, John talks to Komorov about not being around for his family when he needed to be, and that's why Jack resents him. Komorov sympathizes with him, and unbeknownst to both of them, Jack overhears this.
The trio go to a ballroom where they find Irina (Yuliya Snigir) and the key to the file. John is suspicious of her, and he's proven right when Alik and his guys come in. They tie John and Jack up, and Irina turns on her father, holding him at gunpoint. While Alik gets into his whole anti-American spiel, the McClanes free themselves and kill the goons as Alik and Irina escape with Komorov. The McClanes just manage to get out and avoid getting shot at.
John asks Jack what it is that is on that file. He reveals that there is information regarding Chagarin during his and Komorov's time working in Chernobyl, much of which is incriminating, and Komorov plans on using it against Chagarin after a fallout that the two of them had. The two share a moment as John treats Jack, who was wounded from the shootout.
While the villains find the location in Chernobyl with the file, John and Jack steal a car packed with guns and drive there. The villains enter a room with a lot of uranium. When Alik asks where the file is, Komorov comes out and shoots him in the head, then shoots him more times to ensure he's dead. He is revealed as the mastermind behind the plot, and he embraces Irina, who was playing along the whole time. Komorov makes a phone call to Chagarin, showing him that he's won, and Chagarin's masseuse (another goon of Komorov's) chokes Chagarin to death.
Irina and other henchmen are preparing to take off with what they need as the McClanes arrive. Although initially thinking Komorov is still innocent, John and Jack realize he's the true villain, and they learn there was never any file and that Komorov was planning on using the uranium to build powerful weapons. Irina and some goons start shooting at the McClanes, allowing Komorov to run, but John tosses a grenade, killing most of the men and allowing them to run.
Irina gets onto the chopper with some henchmen. John hops into the chopper and kills the henchmen and boards a truck, driving it out of the chopper after delivering his "Yippie-ki-yay, motherfucker" line, weighing the chopper down. Meanwhile, Jack exchanges gunfire with Komorov. Jack gains the upper hand and takes Komorov down before tossing him off the roof, where he is sliced up by the chopper's blades. Irina screams as she sees her father die. John manages to make it back to the roof with Jack, just as a vengeful Irina shoots at them. As she has run out of bullets, she flies the chopper into the building right as the McClanes jump down into a tank of water. The chopper explodes and Irina is killed.
Jack resurfaces but doesn't see John. When he finally calls out, "Dad!" (after referring to John by his name the whole time), John responds. The two walk out from the wreck, and Jack accepts his name as a McClane. He asks John if he always goes looking for trouble, or if trouble finds him. John responds by saying after all these years, he's still asking himself the same question.
The film ends with John and Jack arriving back in America in a jet and being greeted by Lucy. The three of them walk away as a family.
You can send in your spoiler to other movies by going here.