Worricker (Nighy) after the director of MI5 dies. A conspiracy to turn control of MI5 over to the Prime Minister leads Worricker to the islands known as the Turks & Caicos, where he is persuaded by the CIA to deal with a group of ambiguous Americans attending a high-level conference. At the same time, an old girlfriend, Margot Tyrrell, is being asked to betray her boss in London in order to establish an illicit connection between the prime minister and dark goings-on in the war on terror.