In the series conclusion, a furious Stephen vows to bring George Fergus down for planting Sonia in his office. As a result, he offers to give a full, exclusive interview to Cal, but Cal's new editor (Geraldine James) nixes it.
Cal interrogates Stephen's assistant about the hiring of Sonia, which leads to an unexpected discovery; Stephen listens in as Cal questions Dominic Foy; Cameron makes a startling decision in response to pressure from the board.
The spin doctor for Stephen's political party mulls a plan to curb Cal's investigation as the team queries Dominic Foy (Marc Warren) about his ties to Sonia. Andrew Wilson: Michael Feast. Helen Prager: Amelia Bullmore. Della: Kelly Macdonald. Anne: Polly Walker.
Detective Chief Inspector Bell suspects Della is withholding information from him; Della begins to suspect that her life is in danger; and an anonymous fax reveals that Stephen was planning to leave his wife for Sonia.
Part 1 of six. The death of a research assistant who worked for Labor MP Stephen Collins (David Morrissey) leads to questions about the nature of his relationship with her. More questions are raised when her death is linked to the murder of a black teenager the same morning. Cal McCaffrey: John Simm. Della Smith: Kelly Macdonald.