Drama series about the British Security Service. Attempting to stop an Iranian nuclear deal on British soil, Adam is framed for the killing of a mugger, who turns out to be a journalist investigating the Tehran train bomb. Ros fears Adam may have been compromised by his source, the Iranian Special Consul's wife, with whom Adam is conducting an affair. The journalist on the verge of printing the story, Ben Kaplan, might in fact be the one person that can save Adam and the credibility of MI5.