|Series 8, Episode 5|
|Series 08, Episode 05|
|Air Date||27 November 2009|
|Previous||Series 8, Episode 4|
|Next||Series 8, Episode 6|
Walker's death is suspected of being a suicide. Harry, however, is sceptical because of two factors: Walker had set up a meeting with Harry hours before the "suicide" and Michael Braydon (Wade McElwain), a second CIA officer, unexpectedly dies. Eventually, it is revealed Ros's mentor, Jack Colville (Stephen Boxer), is responsible for the death of the second officer and is suspected of killing Walker.
In the guise of giving Ros a memoir to read, Colville plants a bug in the manuscript's binder, and becomes able to access MI-5 records. With the help of the bug, he identifies his next target, former MI-6 agent Roger Maynard (Andrew Havill). Caulfield exploits the presence of Colville to cover up her own acts of treason and murder. After Ros and Lucas fail to save Colville's next target, they realise that two of the targets, Braydon and Maynard, are connected to a Balkans operation that led to the death of Colville's girlfriend.
Tariq creates a mirror of the MI-5 database, allowing Ros to fool Colville into thinking she sanctioned the girlfriend's death. After a showdown between the two, he kills himself realising it is the system, not the officers, at fault. In the end, Lucas discovers that Sarah murdered Walker.