Episode 4

When two MI5 informants in Witness Protection are brutally murdered, it's down to Charlie and Field Office 19 to find out why. Most importantly, Charlie and the team need to find out how the perpetrator was able to trace his victims' new identities.

An investigation by Vik (Christopher Simpson) and Jez (Heshima Thompson) reveals that a loophole in the newly enforced ID cards scheme means a person can be tracked down by the Missing Persons Scheme if they have access to their biometric data. When the team finds that the victims' dental records were stolen, it is clear that this is how they were traced.

Meanwhile, Rachel (Ruta Gedmintas) and Charlie are secretly trying to identify "The Ghost Man", hoping that he can lead them to the traitor within MI5. Rachel goes undercover and, with the help of an old police contact, discovers that "The Ghost Man" is ex-people trafficker Luke Blackwell (Warren Brown). Blackwell knows a lot more than he should but will Rachel be able to get all the information she needs before someone else gets to him?

Background checks on Missing Persons' staff show large payments were made into one employee's account. The employee - Pete Norris (Darryl Clark) - has been providing information to terrorist groups looking to take revenge on informants who have gone into hiding.

With a little "gentle" persuasion, Rob and Jez recover the name of the next target; but time isn't on their side and Kylie (Georgia Moffett) and Jez must race to save the next intended victim's life...