When primary school teacher Gemma Hillman goes missing, DC Martin Young and his surveillance partner Stella arrive to set up their surveillance post in the home of single mum Zoe and her daughter Caitlin. They are watching Gemma’s boyfriend Greg Sullivan, who is prime suspect in Gemma’s disappearance. As Martin watches the street, he uncovers a lot more than Greg’s dirty laundry when it turns out everyone living on the street is hiding their own secrets. Zoe’s initial coldness towards Martin thaws when he shows affection and guidance to Caitlin, stirring up displaced paternal yearnings that he’s missing out on with his own son, Max. And when Martin has to leave his post to help his son in need, Zoe covers for his transgression and they form an illicit bond. After an emotional candlelit vigil for Gemma, all eyes are back on the street as Martin watches on with horror as an unexpected dilemma unfolds before him.

Martin challenges Zoe as to whether Greg is a man who is flailing and innocent, or guilty and acting innocent. Martin begins to identify with the isolated Greg and is increasingly torn between whether he is watching a guilty or a desperate man. Whilst Greg leads the surveillance team to a startling discovery, Martin’s guilt over leaving his post in episode one is now compounded when he is asked to formally ID the woman who broke into Greg’s flat. His friendship with Zoe blossoms as he supports a fractious Caitlin, distraught that her favourite teacher is still missing. Whilst Martin reveals surprising information about Gemma, Greg makes an unexpected move, catching the attention of DCI Conroy. And when Martin witnesses a shocking incident, he looks at another resident of Westbury Street in a whole new light.

With DCI Conroy confident in the case against Greg, surveillance is pulled from Zoe’s flat. Martin follows his instincts and goes on a journey to investigate Carl Tuckman’s murky past in Westport, seeking out a retired detective, Donald Vernon,who sheds new light on the case. On his return to Manchester, Martin refocuses his investigation, making an unexpected appeal and growing ever closer to Zoe. At the police station a surprise visitor makes a startling revelation, and Martin’s growing suspicions are confirmed.

With Carl the new prime suspect and all eyes on the Tuckman House, Martin finds himself backing Zoe when a visit from social services regarding Caitlin’s welfare shocks them both. A distraught Zoe questions her own fitness as a mother, leading Martin to overstep his professional boundaries. It is the day of Gemma’s 30th birthday and the residents of Westbury Street are determined to keep Gemma’s name in the press, holding a birthday lunch in her honour. But Zoe is left reeling when she makes an upsetting discovery and as the birthday lunch gets underway, secrets are unearthed as Zoe clashes with Tim and Kate, Carl comes under fire and Kate shocks the surveillance team when she takes the search for Gemma to a new level.

Martin and Hayley persuade Carl to go undercover to get a confession from Kate, hoping she will confess to the murders of both Anna Boruk and Gemma Hillman. The surveillance team prepare for their biggest operation yet with all eyes on Westbury Street and the Tuckman house. Martin prepares a nervous Carl to coax a confession from his own wife. But just as Martin and Stella believe they are finally edging closer to the truth, Martin is forced to intervene when an unexpected move from Greg leads to devastating consequences. A startling discovery leads Martin to finally uncover the events of the night Gemma disappeared and the ground falls from beneath his feet.