Live Free or Die Hard (released as Die Hard 4.0 or Die Hard 4 outside North America) is the fourth installment in the Die Hard film series. It stars Bruce Willis as John McClane, the protagonist of the first three films. The film takes place some 19 years after the first film, and sees McClane face a gang of virtual terrorists. The film's American and Canadian release date was June 27, 2007.[2] The film was based on the 1997 article A Farewell to Arms written for Wired magazine by John Carlin.[3]

At the start of the film, a terrorist begins as an attempted security breach on an FBI facility system is successful, and computer hackers are assassinated by the terrorist mastermind Thomas Gabriel (Timothy Olyphant) instead of being paid for their collaboration. The FBI, unaware of the killings, dispatches NYPD Police Detective John McClane (Bruce Willis) to visit a known hacker, Matthew Farrell (Justin Long), as part of their investigation regarding the breach. Gabriel's henchmen attempt to assassinate McClane and Farrell, but their targets escape. McClane transports Farrell to the FBI's Washington DC headquarters and its head, Assistant Director Bowman (Cliff Curtis), in the midst of a shutdown of the traffic system in DC. The stock market is manipulated shortly afterward, causing it to crash.

McClane is ordered to take Farrell into protective custody, and Gabriel sends more henchmen to kill the pair. McClane and Farrell evade their assassins again, and as the country's infrastructure is threatened with a major break down, Farrell tells McClane the terrorists are initiating a fire sale and that major utilities would be next. The detective and the hacker travel to a power hub in West Virginia to defend it, finding that the terrorists are already there. McClane battles terrorists while Farrell undoes the damage done to the computer system. They are contacted by Gabriel, who finds out that McClane has killed his lover Mai Linh (Maggie Q) and angrily re-routes gas lines to destroy the hub in a gas explosion. The McClane and Farrell escape once more, and on Farrell's advice, the pair visit his hacker friend the Warlock (Kevin Smith) for help. At the Warlock's home, they find out about Gabriel's background and attempt to hack into the terrorist's systems. Gabriel contacts the detective at the Warlock's home via webcam, and he shows that he has McClane's daughter Lucy (Mary Elizabeth Winstead) as a hostage. While McClane distracts Gabriel in conversation, the Warlock determines Gabriel's location, at a hijacked NSA building.

McClane and Farrell travel to the NSA building, and the detective combats terrorists while Farrell discovers and tries to undo Gabriel's plan to steal backup financial information from servers in the building. Farrell is able to lock the terrorists out of their server hack, rendering the task incomplete, and the he is taken hostage by the terrorists. With McClane after them, Gabriel and his henchmen flee the building with their hostages. McClane manages to hijack one of the escaping trucks and pursues Gabriel and the hostages. Gabriel renders a hack to deceive the pilot of a F-35 Lightning II jet to attack McClane's truck. The jet engages McClane, but the detective is able to escape. He tracks Gabriel to a warehouse, where the terrorist is forcing Farrell to undo the encryption at gunpoint. McClane is shot upon arrival and Gabriel says that he will kill them when it's over. Proding McClane's wound with a gun, Gabriel taunts "on your tombstone will read, always in the wrong place at the wrong time". McClane then delivers the classic catchphrase, "how about, Yippee-Ki-Yay, motherfucker", and squeezes the trigger, firing a bullet through his shoulder and into Gabriel's heart, killing Gabriel instantly. Farrel jumps up and shoots the thug holding Lucy just as backup arrives along with paramedics who tend to their wounds.