Ros is taken hostage as part of a siege at the Saudi Trade Centre. The hostage-takers demand that Al-Qaeda prisoners are released.
MI5 realise that there's an informant among them. The leak is traced to Neil, who commits suicide. But Adam is suspicious - why would Neil be helping an Arab terrorist group when his family were killed by Arab suicide bombers?
The team soon realise they're actually dealing with an Israeli plot designed to discredit the Saudis and de-rail the nuclear deal.
The Security Services storm the Embassy. The true nature of the plot remains a secret and the world believes an Al-Qaeda plot has been foiled. The nuclear deal with Saudi Arabia goes ahead, with the Saudis lauded as a worthy ally who stand firm in the face of fundamentalism.