A neo-conservative group murder an ex-minister to cover up his past and then they hunt down the journalist who is threatening to blow the story and is under MI5 protection.

The Syrian foreign minister tries to establish subversive contacts with MI5 at the opening of a cultural centre in London. Fiona is desperate to lead this mission and must confront her Syrian past.

Adam and Zaf try to find a group of terrorists who have infiltrated Britain. Ros oversees a visit by a delegation of Saudi princes offering a guaranteed oil supply in exchange for nuclear expertise, but the Saudi Trade Centre is attacked by terrorists.

The terrorists start to execute hostages in pursuit of their demand for the release of Al-Qaeda prisoners held in Saudi Arabia, but suspicion arises as to the true identity of the terrorists.