In the near future, energy wars are raging across the globe, blackouts are a regular occurrence, and the privileged Citizens and the desperate Outsiders of London live very separate lives. Hunter is a Citizen whose father works for the government; yet he cannot help being fascinated by the Outsiders' ingenuity and, in particular their mastery of free running. When he meets Uma, an Outsider, he is quickly drawn into her world and finds himself racing against time—and against the government's cruel Kossak soldiers—to protect everything the Outsiders hold dear.