But as CCTV footage puts the detectives initial prime suspect out of the picture, a bitter rivalry between the victim and a single parent reveals a whole new side to the case.
But when the accused's daughter makes a shocking confession to the detectives, they suspect her parents are conspiring to prevent her from obtaining a criminal record and losing her place at university.
Despite a criminal record full of robbery offences, Preston and Shaw are doubtful over the roofer's guilt — and when the victim's son-in-law is revealed to have had a serious gambling addiction, the focus of the investigation soon changes.
The detectives face a race against time to catch the offender, but after identifying their prime suspect, they uncover a complex web of lies including theft, fraud and illegal marriage.
Although they initially struggle to find a motive for the attack, despite interviewing a jealous former business partner and the victim's alcoholic mother, it soon transpires that a former lover, who believes he could be the father of her three-year-old son, may be responsible.
As the victim comes under pressure from his bosses to drop the charges to prevent an investigation into their suspect methods, the accused puts her ex-boyfriend in the frame for the crime.
The victim has awoken to find the word 'Tart' written on her forehead, and when the detectives discover that photo evidence of the assault has gone viral, they try to determine which of her so called-friends is responsible.
When a hit-and-run leaves cyclist Marcus Haigh in an induced coma, Preston and Shaw find themselves on the trail of respected businessman Richard Booth, who claims to have no recollection of being involved in the incident; and has no solid alibi for his whereabouts at the time.
When a campaign of harassment against nurse Alice Dixon culminates in the destruction of her clothes and personal photos, Preston and Shaw uncover a complex web of relationships and a trail of evidence which points the finger at her flatmates: Polly, Jeremy and Adam.