Will Sawyer, a U.S. Marine war veteran and now an FBI Hostage Rescue Team (HRT) leader, loses his left leg below the knee when he and HRT colleague Ben Gillespie encounter a hostage taker with a suicide bomb.

Ten years later, Sawyer is a private security consultant who, on a recommendation from Gillespie, is hired to review security for the world’s tallest skyscraper, Hong Kong’s 3,500 foot, 225 floor tower, “The Pearl”, for owner Zhao Long Ji. Sawyer is joined by his wife, Sarah, and twin children, Georgia and Henry, staying with him on the not-yet-opened residential floors.

Sawyer meets with Zhao, Gillespie, security director Okeke and head insurance underwriter Pierce, to report that the computerized fire and security systems have passed his tests, though he needs to inspect the offsite security center. Zhao provides him with a tablet that gives Sawyer complete control over the Pearl’s systems. Sawyer and Gillespie head to the offsite facility, but a thief hired by international terrorist Kores Botha attempts to steal the tablet. Gillespie reveals he is also working for Botha and attacks Sawyer for the tablet, ending with Gillespie’s death.

Botha and a group of his men break into the Pearl and undermine the safety systems by using a water-reactive chemical to start a fire on the 96th floor, creating a barrier preventing entry to or exit from the upper 130 floors. Sawyer tries to return to the Pearl, but is attacked by Xia, one of Botha’s associates. Xia and her agents take the tablet and kill everyone at the offsite facility, then use the tablet to disable the fire-extinguishing systems in the Pearl and then activates the air vents to spread the fire to the upper floors.

Zhao and Okeke send security guards to rescue Sawyer’s family, but the guards are killed by an explosion and the family is believed dead. Urged on by Pierce, Zhao orders the remaining personnel to evacuate via helicopter, but Pierce reveals he is also an agent for Botha, killing all but Zhao, who escapes into his penthouse apartment, locking it down from any intrusion.

Inspector Wu leads the local police to secure the Pearl and capture Sawyer, who is believed to be behind the incidents. Sawyer evades them and makes his way into the Pearl above the fire barrier via construction equipment from a neighboring building. Sawyer kills Pierce before Pierce can kill Sawyer’s family, though Georgia is separated from the others. Sawyer has Sarah and Henry ride through the fire barrier in a free-fall elevator before applying the emergency brakes, letting them escape safely; Sarah immediately explains the situation to Wu and that Botha’s men will likely escape via parachute to a nearby landing zone.

Sawyer searches for Georgia, finding she has been captured by Botha, who demands Zhao in return for Georgia. Sawyer is forced to scale the outside of the building to access the security panel for Zhao’s penthouse, then enters and confronts Zhao. Zhao explains that Botha had extorted money from him during the $6 billion construction project. When Botha learned that Zhao kept a detailed computer file of the transactions, which can reveal accounts and names of three crime syndicates Botha works for, the attack was instigated to get the records.

Sawyer brings Zhao to Botha at the top of the skyscraper, acquiescing to the trade for Georgia. However, Zhao distracts Botha, allowing Sawyer and Zhao to kill Botha’s thugs. Botha grabs Georgia and threatens to drop her off the building, but Sawyer beats him, rescues Georgia, and lets Botha die in a grenade explosion as he falls.

Wu leads an attack on the likely dropzone, securing Xia and killing her thugs. Sarah recovers the tablet and uses it to restart the Pearl’s systems, extinguishing the blaze. Sawyer, Georgia, and Zhao are brought down safely by helicopter, and the Sawyer Family happily reunites. Zhao states his intention to rebuild the Pearl, shown to have massive fire damage that extends from the 96th floor to the top of the building.