Four years after the events of Day 8, Jack Bauer remains a federal fugitive. Meanwhile, amid growing concerns over the use of US military drones in combat, President James Heller pays a historic visit to London to negotiate a treaty to continue their basing on British soil. Having heard rumors of an imminent attack against Heller, Bauer resurfaces in the city, where he is apprehended by the CIA and forcibly recruited into joining their investigation, with the promise of amnesty in return for his co-operation. As forces within the White House conspire against him, Bauer realizes that the complexity of the plot extends beyond a presidential assassination, and that the consequences of a successful attack will alter the course of history. With the help of a disgraced CIA agent and a hacker collective preaching free information, he must confront an unseen enemy whose personal vendetta threatens to push the world to the brink of war.