Suspects

The team investigate the brutal attack and subsequent death of popular art teacher Abigail Lincoln at the college where she worked. Initial suspicion falls on the college caretaker, who has a conviction for stalking and assaulting a former girlfriend, and with whom Abigail had recently argued. However, it soon transpires that Abigail held information on an inappropriate relationship between a pupil and a member of staff. When headteacher Rory O'Hanlon's fingerprints are found on the weapon used to attack Abigail, it soon transpires that he was having a sexual relationship with pupil Melissa Parker. Jack also discovers O'Hanlon is connected to several unsolved murders.

The team investigates the case of a badly burned young woman, Sian Jenkins, who is found dumped two years after she was reported missing. DNA underneath her fingernails is discovered to be that of a fellow missing person, Josie Wilson, who disappeared in 2005 at the age of eight. Jack suspects that Sian's father, Neil, may have had a part to play in her disappearance after evidence suggests that he accosted a young homeless girl, during his rounds as a charity worker. Martha, however, isn't convinced, and soon evidence suggests that Josie's father, Mike, may infact be the abductor, and the discovery of a baby in his cellar unravels a string of horrific events.

The team investigate a petrol-bomb attack in which 19-year-old Asif Khan is badly injured. His father, Jamaal, has been involved in a bitter row with reprobate property developer Gregor Forrester, and old enemy of Jack and Martha's, who has so far managed to elude conviction. Fingerprint evidence suggests that a familial relative of David Eboda, Forrester's right hand-man and former ex-cop and mentor to Jack, is the personal responsible for the attack, but a full DNA profile of Forrester's son, Zak, identifies him as the culprit, and reveals that he is Eboda's son, not Forrester's. When Zak mysteriously disappears, Jack decides to press Eboda to lead him to the truth.

The body of a young girl is found naked and severely wounded on a patch of wasteground, leading Charlie to suspect the victim is Mandy Grainger, who parents reported her missing earlier in the day. When the victim is identified as male - Jez Collins, a post-op transgender - the team suspect that he may have been Mandy's boyfriend. With Mandy still missing, the team discover evidence which links both victims to a house party the previous night, but when Jack interviews homeowner Emily, she denies all knowledge of the pair. When it transpires that Mandy is also in the process of change from girl to boy, the focus of the investigation soon turns towards Mandy's father.