On Christmas Eve, NYPD Detective John McClane arrives in Los Angeles, hoping to reconcile with his estranged wife, Holly, at a party held by her employer, the Nakatomi Corporation. He is driven to Nakatomi Plaza by limo driver, Argyle, who says he will wait for McClane in the garage. While McClane changes his clothes, the tower is seized by a German radical, Hans Gruber, and his heavily armed team, including Karl and Theo. Everyone in the tower is taken hostage, except for McClane, who slips away.
Gruber is posing as a terrorist to steal the $640 million in untraceable bearer bonds in the building's vault; he tries to get executive Joseph Takagi to reveal the access code but Takagi refuses; Gruber executes him and tasks Theo with breaking into the vault. McClane witnesses the murder and one of Gruber's group, Tony, is sent after him. McClane kills Tony and takes his weapon and his radio which he uses to contact the skeptical Los Angeles Police Department (LAPD); Sergeant Al Powell is sent to investigate. McClane kills two terrorists and discovers a bag of C-4 and detonators. Powell, having found nothing amiss, is leaving when McClane drops a body onto his car. After Powell calls for back up, a SWAT team attempts to storm the building but is assaulted by the terrorists. McClane throws some C-4 down an elevator shaft, causing an explosion that kills some of the terrorists and ends the assault.
Holly's co-worker Harry Ellis attempts to negotiate on Gruber's behalf, but when McClane refuses to surrender, Gruber kills Ellis. McClane catches Gruber checking explosives on the roof but he pretends he is an escaped hostage and McClane gives him a gun; when Gruber attempts to shoot him, he finds it is not loaded. Gruber is saved by the intervention of other terrorists. McClane escapes but is injured by shattered glass and loses the detonators. Outside, FBI agents take control; they order the power to be shut off which, as Gruber had anticipated, disables the final vault lock so his team can collect the bonds.
The FBI agrees to Gruber's demand for a helicopter, intending to send gunship helicopters to eliminate the group. McClane realizes Gruber plans to blow the roof to kill the hostages and fake his team's deaths. Karl, enraged by the death of his brother Tony, attacks McClane and is apparently killed. Gruber sees a news report by reporter Richard Thornburg on McClane's children and deduces that he is Holly's husband. The hostages are taken to the roof while Gruber keeps Holly with him. McClane drives the hostages from the roof just before Gruber detonates it and destroys the approaching FBI helicopters. Meanwhile, Theo retrieves a van from the parking garage but is neutralized by Argyle, who has been following events on his car radio.
A weary and battered McClane finds Holly with Gruber and his remaining henchman. McClane surrenders to Gruber and is about to be shot, but grabs a concealed pistol taped to his back and uses his last two bullets to wound Gruber and kill his accomplice. Gruber crashes through a window but grabs onto Holly's wristwatch. Gruber makes a last-ditch attempt to kill the pair as McClane unclasps the watch and Gruber falls to his death.
Outside, McClane and Holly meet Powell. Karl emerges and attempts to shoot McClane but is killed by Powell. Holly punches Thornburg when he attempts to interview McClane. Argyle crashes through the parking garage door in the limo and leaves with McClane and Holly.
Bruce Willis as John McClane,
Alan Rickman as Hans Gruber,
Alexander Godunov as Karl,
Bonnie Bedelia as Holly Gennero-McClane,
Reginald VelJohnson as Al Powell,
Paul Gleason as Dwayne T. Robinson,
De'voreaux White as Argyle,
William Atherton as Richard Thornburg,
Clarence Gilyard as Theo,
Hart Bochner as Harry Ellis,
James Shigeta as Joseph Yoshinobu Takagi,
Additional cast includes Gruber's henchmen: Bruno Doyon as Franco, Andreas Wisniewski as Tony, Joey Plewa as Alexander, Lorenzo Caccialanza as Marco, Gerard Bonn as Kristoff, Dennis Hayden as Eddie, Al Leong as Uli, Gary Roberts as Heinrich, Hans Buhringer as Fritz, and Wilhelm von Homburg as James. Robert Davi and Grand L. Bush appear as FBI Special Agents Big Johnson and Little Johnson, respectively, Tracy Reiner appears as Thornburg's assistant, and Taylor Fry and Noah Land make minor appearances as McClane's children Lucy McClane and John Jr.