Banning (Gerard Butler) is an agent of the U.S. Secret Service. Recently, he received an important task, that is, to join forces with Director Lyn (Angela Bassett) to escort President Benjamin (Aaron Eckhart) to St. Paul's Church in London to attend the funeral of the British Prime Minister. The British Prime Minister died strangely. Banning and Lyn knew that their trip must have been closely watched by criminals. At the same time, at the funeral, heads of state attended, and the prosperous and beautiful city of London instantly became the focus of world attention. Sure enough, the assassins lurked in the dark waiting for the opportunity, national leaders were repeatedly ambushed, London's landmark buildings were not spared, and the whole city fell into chaos and paralysis. For Banning, the most important task is to escort the president back home.