Former U.S. Army Ranger Mike Banning (Gerard Butler) is now a Secret Service agent assigned to head the Presidential Detail. He maintains a personal, friendly relationship with President Benjamin Asher (Aaron Eckhart), First Lady Margaret Asher (Ashley Judd) and particularly their son Connor Asher (Finley Jacobsen). On a drive from Camp David on the snowy night of December 22, 2010, the car transporting the President and First Lady crashes; Banning saves Benjamin, but Margaret dies.
Eighteen months later, Banning works at the Treasury Department within eyesight of the White House, and wants to return to being a Secret Service agent on the Presidential detail, but Asher does not allow this as Banning brings up memories of the night Margaret died. During a meeting at the White House on July 5, 2012 between Asher and the South Korean Prime Minister, a Korean group leads a guerrilla attack against the White House. The assailants include an airplane attack against Washington D.C. by a stolen USAF AC-130 gunship, land forces disguised as citizens which initiate a car bomb attack, traitors within the security detail of the South Korean Prime Minister, and the current head of the Prime Minister’s Detail, Dave Forbes (Dylan McDermott), who reveals himself to be a traitor. The assault ends with the Koreans capturing the White House and holding the President and several top officials hostage in the White House bunker, where they kill the South Korean Prime Minister. Agent Roma (Cole Hauser) informs Lynne Jacobs (Angela Bassett), the head of the Secret Service, that “Olympus has fallen” before getting killed.
The group is lead by Kang Yeonsak (Rick Yune), an ex-North Korean terrorist who appears to hold allegiance to neither North nor South Korea but to the concept of a unified Korea by any means. Kang has two goals. The first is to use the President as a hostage to force the United States to withdraw from Korea, allowing the civil war to finish. Second, he seeks to detonate all United States nuclear bombs in their silos and destroy the United States as revenge for the death of his mother, victim of an American landmine, and his father who was executed. To accomplish this, he requires the access codes to a system in the bunker called Cerberus, which are held by three top United States officials within the bunker, including the President. Asher orders the other two officials to reveal their codes to save their lives, certain that he will not give up his code.
During the assault, Banning sneaks into the White House and is the only defending survivor. He gains access to the President’s satellite ear phone, which he uses to maintain contact with Allan Trumbull (Morgan Freeman), the Speaker of the House who is now the acting President. His first act is to save Connor, who Kang plans to use to force Asher to reveal his Cerberus code. He finds Connor hiding in the walls thanks to the training Banning had given him, and sneaks him out of the White House through the vents. Banning then goes on a mission of obtaining information on the assailants and reducing their numbers. He also kills Forbes, who has realized his error and repents before dying, helping Banning by reporting him dead to Kang.
When Kang tries to execute Secretary of Defense Ruth McMillan (Melissa Leo), Banning is able to save her and take out several more of Kang’s men in the process. With Kang’s forces now greatly dwindling, he fakes his own death, as well as Asher’s, by sacrificing several of his men and the other remaining hostages. Kang, Asher, and the few remaining terrorists remain in the bunker, unknown to the outside world. Kang eventually cracks Asher’s code and activates Cerberus as Banning realizes that his apparent suicide was faked. As Kang attempts to escape Banning kills off the remaining terrorists and manages to kill Kang in a knife fight by stabbing Kang in the head, before disabling Cerberus with the assistance of Trumbull, and one of Trumbull’s team members who gives him the deactivation codes. Banning and Asher safely escape the White House, the United States begins repairing the damage to Washington D.C. and the White House, with Banning once again becoming head of the Presidential Detail.