Greg Walker

Greg Walker is a major character from the Series 17 episode Coup de Grace. He is a defense lawyer and Nikki Alexander's love interest. He is later revealed to be a serial killer, who framed his client David Bennetto for his crimes.

Background
Greg was married, but he and his wife struggled to conceive, due to Greg's infertility, which took its toll on their relationship. They eventually adopted a baby girl, but ended up separating. Greg began murdering young men, torturing them, repeatedly asphyxiating and reviving them and finally shooting them, getting off on the feeling of power that came with dominating his victims. His reasons for killing are not explicitly stated, but given is infertility, it is possible he felt a loss of masculinity and took it out on his victims.

After killing his first victim, the man's boyfriend David Bennetto, a mentally disturbed former soldier, was suspected of the killing. Greg took advantage of this, seeking out David and becoming his lawyer, so as to learn his habits and frame him for his crimes. As a result, Greg got away with murdering another man, before David was charged and found guilty of murder. Greg remained his lawyer, campaigning to try and get David released (presumably so he could use him as a cover to kill again).

Coup de Grace
Greg contacts Dr Nikki Alexander and asks her to give evidence for the defense to try and have David'd conviction quashed. Nikki's expert testimony helps persuade the judge to acquit Bennetto. Greg and Nikki appear to be attracted to one another, flirting, going for drinks and also sharing a kiss. Greg begins killing again, and again, Bennetto is the prime suspect. Whilst on a date with Nikki, Greg receives a call from a distraught David, and the pair go to David's apartment. There, Greg tries to calm David, who reveals he has found his father's old gun and wants to give it to Greg to hand over to the police. Unfortunately, things go awry when Nikki accidently finds the gun first and, fearing the worst, calls Thomas Chamberlain. She is discovered by David, who panics and takes both Nikki and Greg hostage.

Greg manages to get through to David, convincing him to give him the gun. When David attempts suicide by cop, Greg pushes him out of the way and helps Nikki tend to his shoulder injury. He later confronts DI Rachel Klein over her actions, saying her tunnel vision is impeding the investigation and has driven a mentally ill man to suicide (although Greg's motivations are purely selfish, he does have a point). He subtly manipulates Nikki into backing him up; Jack Hodgson sees through him and warns Nikki that Greg is playing her, but Nikki refuses to listen. Greg invites Nikki out to lunch, but she becomes disillusioned with him when she sees him being dropped off by his estranged wife, with their daughter in the car. Greg explains his situation to Nikki, but she is still upset with him.

Nikki gradually pieces together the clues and realises that Greg has been the murderer all along. Klein has her call Greg in an attempt to trace the call; Greg receives it whilst sitting in his van, apparently waiting for another victim. He guesses part way through the conversation that Nikki knows the truth, he comments that she was "the only one who could've figured it out" before hanging up. The police and forensics team rush to Greg's location and order him to get out of the van. Knowing it is all over for him, Greg pulls a gun on the police, prompting them to shoot him, despite Nikki's warning that this is exactly what he wants. However, Nikki is able to resuscitate Greg (ironic, considering that this is what he did to his victims) and he is last seen strapped down on a stretcher, being loaded onto an ambulance. After being treated for his injuries, he was presumably incarcerated.

Modus Operandi
Greg targeted young men, most of whom were gay, though Nikki points out that this is probably coincidental, as Greg's motivations for killing are based on power and dominance, with sexual orientation having little to do with it. He would drug his victims using sedatives (the same prescribed to David Bennetto to treat his depression and PTSD, only in much higher dosages), then torture them by cutting them with a knife, masturbating over them and repeatedly asphyxiating then resuscitating them. He would then finish them off with a gunshot to the head, leaving their bodies in marshland. He drove a dark blue van in all his crimes.

Greg would frame his client, David, for the murders, subtly manipulating David into incriminating himself and also taking advantage of the fact that David was mentally unstable, had a relationship with the first victim and a homophobic father and took sedative drugs to further make him seem guilty.