The novels revolve around three teens who are recruited by an agency known as 'The Agency' moments before their deaths. The Agency was set up to protect the established set of events throughout history and to fix it if it is tampered with. They operate from their field office underneath an archway of the Williamsburg Bridge in New York City in a two-day 'Time Bubble', on 10 and 11 September 2001. Each novel revolves around a major change in the historical timeline and the team must work with each other to fix it with the help of their 'support units' – cyborgs who can mimic human behaviour. Later in the series the characters move to a second base under the Holborn Viaduct in Victorian London.