As Annie becomes more entrenched in the investigation, Alan feels increasingly marginalised and their relationship begins to suffer. College Principal Craig Petrie is questioned as the main person of interest. Petrie is connected to both victims, but he also throws doubt on Leighton's alibi during the time of the murder and Annie is forced to investigate. Other lines of enquiry include the stolen van in which the body was found. When a hair is discovered in the van, one not belonging to the victim, the hunt to find the driver escalates… As evidence mounts against Petrie, Quigley agrees to allow Albrighton into the interview to help crack Petrie's composure. But things take a downward spiral when Petrie turns the tables on Albrighton, goading him about a personal tragedy. Albrighton assaults Petrie leaving Quigley with no choice but to release the prisoner.