DCI Gill Murray was the former head of Synicate 9. An old friend of Janet's, she was a police officer for 30 years. She worked in the Agency, all the time ignoring her husband's infidelity before he got a uniformed police officer who was much younger pregnant. The couple had one son, Sammy.

A professional, by the book but intuitive and knowledgeable detective who does the job properly though she is unafraid to defend and protect her detectives, Gill respects Rachel even if the younger woman does very stupid things, though she forgave the younger woman for PNCing Nick Savages' car (an offence which would have gotten Rachel sacked).

In series 3, Gill was kidnapped by a deranged Helen Bartlett, who had been the focus of an investigation involving her parents, the Bevans. The Bevans had kidnapped and sexually assaulted numerous people in the past, and they had murdered them and buried their remains in the basement of their house. Helen's two siblings, Sheila and Michael, were also victims of Joe and Eunice Bevan's depraved ways. Helen was later arrested when the CPS decided to charge her. Afterwards her life became a living hell with people spitting on her and pushing dog mess through the letterbox, and eventually leading to the breakup with her girlfriend.

Helen kidnapped Gill after the latter had made the mistake of leaving the car door unlocked while she was shopping at the supermarket to grab some food and drink for her son's engagement party. Helen overpowered Gill, wrapped her head to the headrest with a belt and forced her to drive to Flamborough Head, where she then proceeded to kill herself.

A year later Gill announced her retirement, but unknown to all until much later she had begun to drink alcohol to cope with the stress of the job. Rachel, her last DS after Rob Waddington had left, noticed the bottle of gin on her desk, a mistake Gill would never in the right frame of mind have made. Later on during the stress of her final case, Gill made the mistake of drinking again at the magistrates court where the sly and devious Evie Pritchard was taken before the magistrate for running a slavery ring.

Evie smelt the gin on her breath and instantly filmed a video and posted it online and was later watched by Rachel and Janet and presumably other members of the police. In the end, Gill was allowed to retire when Evie was finally charged with murder.