The murder of an MP's researcher leads journalist Cal McCaffrey to uncover a complex thriller revealing the links between government and big business.
When Sonia Baker, a young political researcher, is killed on the Tube her high profile Labour MP boss (David Morrissey) is devastated. The press smell blood and questions are asked about the nature of his relationship with Sonia.
The story is pursued by The Herald, its editor Cameron Foster (Bill Nighy) and its reporter, Cal McCaffrey (John Simm), who was Stephen's former campaign manager. Cal is uncomfortable with pursuing what amounts to a domestic scandal until his colleague Della (Kelly Macdonald) discovers a surprising link between Sonia's death and the murder of black teenager, Kelvin Stagg.
Kelvin had stolen a silver briefcase that contained photos of Stephen and Sonia and a gun. A courier shot at the same time as Kelvin is recovering in hospital when DI Brown, who is in charge of the case, visits him, as does Della. The hospital fire alarm is set off and as they are moving the patient a marksman takes arm at him but misses and kills DI Brown.
After the murder of DI Brown, DCI Bell (Philip Glenister) is put on the investigation. He knows Della is withholding information and is determined to find out what she and Cal know.
Meanwhile, Stephen Collins' story becomes more complicated when an anonymous fax reveals that his affair with Sonia was far from being a superficial thing - Stephen was going to leave his wife Anne (Polly Walker) for her. This doesn't go down well with the party's spin doctor, Andrew Wilson (Michael Feast), who is trying to keep Stephen's reputation intact. Della realises she is being followed and that her life is in danger.
DCI Bell and Cal collude in a plan to smoke out the hit man. Meanwhile, his team pin the author of the anonymous letters to a City wideboy named Dominic Foy (Marc Warren). The discovery that he had a sexual history with Sonia leads the team to suspect that he's guilty. Stephen may also be hiding something as Sonia knew she had the job in his office a month before her interview.
Meanwhile, Cal's personal and professional life gets hopelessly tangled when he embarks on a love affair with Anne Collins.
This leads Stephen to tell Andrew Wilson to leak the information to the press and ruin Cal's reputation. His only supporter now is the energy minister, George Fergus, who wills him to succeed.
Cal and his team corner Dominic Foy, who is edgy and obstructive and constantly changes his story. They discover a connection between Foy and lobbyists for the oil industry.
Stephen's defence over the hiring protocol of Sonia leads Cal to interrogate his obtuse assistant Greer (Deborah Findlay) who finally admits to being influenced by an unexpected source. When the UK's largest oil company gets wind of where The Herald's investigation is heading, Cameron finds himself under pressure from his board and makes a startling decision.
Sensing that his team is close to snaring their prey, Cal invites Stephen to listen in to an interview with Dominic Foy, hoping that with a few well-aimed questions, the increasingly paranoid Foy will crack. He's right - Foy's confession is a goldmine, but it sends Stephen over the edge and Foy to casualty.
On the morning Cameron's explosive headlines hit the newsstands, Cal travels to Manchester to see Anne. He is disturbed to find her supportive of Stephen when he reveals that Sonia had been planted in his office.
Stephen is now single-minded in his obsession - who in the government knew Sonia was a plant? And why are they protecting George Fergus? His anger at the scale of the deception leads him to Cal once more. But the paper's executive editor puts the brakes on the story, leading Cal and Cameron to hatch a plan to print it. With the stakes at the highest, their story takes one final, gut-wrenching turn.
