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.