|Character Profile||List of appearances|
DS Gavin Armstrong met with DS Geoff Thorpe to inform Patrick Blake's daughter, Sienna that Gavin will be taking over the investigation into Patrick's disappearance. Geoff then reveals that they have found some new evidence, intriguing Sienna. Gavin and Geoff take Sienna to the woods, where they reveal that her daughter and Patrick's real murderer, Nico Blake, as their new witness. Gavin reveals he believes that Patrick's wife, Maxine Minniver, was the person who murdered Patrick, and Sienna agrees to help the police get a confession from Maxine. Gavin later reveals to Sienna that Maxine's boyfriend, "Mike Jones", is Warren Fox and Sienna persuades Warren to help them get a confession from Maxine.
Gavin develops a sudden attraction to Leela Lomax, who begins receiving sinister messages. Leela immediately reports this to the police and Gavin takes charge of the case. Gavin implies to Leela that her friend, Zack Loveday, could be stalking her, which Leela assumes. Gavin provides Leela with her stalker's number and when she calls it, the phone rings in her daughter, Peri Lomax's bag. Peri denies any involvement and Gavin concludes the stalker planted the phone on Peri. He later claims that Leela's former husband, Cameron Campbell, who is a serial killer, has escaped from prison, with the Lomax family losing their electricity shortly after. Gavin fixes their electricity and claims Cameron had been hiding and never escaped. Leela thanks Gavin and it is revealed that he is stalking Leela and watching her after planting a virus on her laptop.
Gavin later deliberately interrupts an intimate moment between Leela and Zack. Following the murder of Amy Barnes, Gavin arrests her former partner, Ste Hay and makes him confess to her murder. Gavin supports Leela and they have sex, although Leela rejects him the following day, claiming it to be a mistake. Frustrated, Gavin graffitis Leela's wall, which Leela reports to the police. Gavin's colleague and Amy's widower, Ryan Knight, takes a statement from Leela and realises Gavin is her stalker, but decides not to report it at risk of Ste being acquitted of Amy's murder. When Gavin plants spray paint in Zack's bag and arrests him, Ryan releases Zack from custody and tells Leela that a man serving jail time is her stalker, before warning Gavin and telling him to take sick leave and seek psychiatric help. However, as he is leaving, Gavin watches Leela through his hidden camera.
Gavin returns two months later just as Leela and Zack are about to reunite. A jealous Gavin pushes Zack down the stairs outside the Lomax house. Zack is rushed to hospital where he says he was pushed. Zack's father, Louis Loveday, reports this to Gavin who promises to find Zack's attacker as he is clearly dangerous. Gavin breaks into Leela's flat, stealing a photo of her and her nightgown. However, when Leela reports the theft to him he slips up by revealing information he wasn't supposed to know. Leela confronts Gavin who blackmails her into silence by threatening to tell Zack that Louis is Daniel Lomax's biological father.
Gavin then turns his attentions to Dirk Savage's wife, Cindy. He moves in with Dirk and Cindy as a lodger, sets up a fake website with nasty messages about Cindy and then plays the role of the hero. Gavin then arranges for Dirk to receive a false telephone call claiming that his daughter, Liberty has been in an accident. After Dirk leaves, Gavin persuades Cindy to attend a conference in Liverpool. Gavin accompanies Cindy to protect her, having booked adjacent rooms at the hotel for Cindy and himself. When Cindy realises the conference is a fake, Gavin convinces her that she should stay in a locked room with him for her safety. Gavin deliberately spills wine on Cindy's dress and tries to kiss her. Cindy rejects Gavin's advances, reminding him she is married to Dirk. While in the bathroom, Cindy receives a phone call from Leela warning her that Gavin is her stalker. Cindy escapes the hotel and Gavin is arrested but later released on bail.
Milo Entwistle visits Gavin in prison, where Gavin threatens to reveal Milo's secret unless he brings him Cindy's nightie. When Milo does deliver, Gavin discovers that it is the wrong one, so he threatens Milo again, getting him to hack into the prison system and forge a document to get him released. After Gavin is released, Cindy and Leela walk into Nightingale's restaurant and stand up to him. Gavin falls for a trap set by Milo, but manages to escape and tries to attack Milo. Milo threw Gavin to the floor, tangling him in Christmas lights and started throwing pots and pans at him. Milo picked up a pot with water inside and threw it at Gavin, causing the lights to spark and electrocute Gavin, also causing a power outage.