Insurance investigator William Byfield is found gassed in his car after he has sparred with Nikki over a claim for terminally-ill suicide Sally Craven. He was also perturbed about the suspicious death of one Stephen Connelly, which leads to Leo being accused of falsifying the post mortem by William's successor, Clare Ambler. In fact Connelly's details never reached Leo and his widow, bereavement counsellor Rebecca, is not only uncooperative with Clare but is Harry's current girl-friend and overly friendly with coroner's officer David Levin. When it appears that William Byfield was murdered Harry suspects Rebecca of being involved.

Now Leo is under investigation by the police over the discrepancies in Stephen Connelly's file. He think he's found the solution when he notices similarities between the Coroner's file on Connelly and another case he had worked on. Harry is convinced that his new lover Rebecca, Connelly's widow, has nothing to do with the apparent forgeries Leo has found. He believes that the fraud is taking place at the Coroner's office and focuses on David Levin, who had access to the information. After Leo is assaulted outside his home, he is hospitalized and in a coma. On the edge of death, Nikki and Harry learn they may have a major decision to make. When the police find Leo's blood in Rebecca Connelly's home and Levin's body in the boot of her car, they are convinced they have the killer. No one however realizes the true deception that is taking place.

The team attend at the apparent suicide of student Jason Renfrew at the local university. The Dean tells Leo Jason complained to her about racist bullying and he is found to have swallowed a chip containing photos of the alleged bullies, as well as having a handgun in his locker. Soon afterwards a gunman goes on the rampage, killing several people including the policeman investigating Jason's death. Nikki and Harry are trapped in a classroom with some students, one of whom, the mortally wounded Matt Frisk, was one of Jason's tormentors. Commander Somerville leads the police team who release them though it is Harry who finds the severely injured gunman. However, he fails to spot the bomb planted on campus.

Harry suspects that Scott Weston, the injured gunman, was shot by another person and it becomes obvious that two guns were used in the massacre. Scott's mother tells Dean Mears that Scott and Jason were good friends, Scott looking out for the more fragile Jason. Meanwhile Nikki is held prisoner in the deserted mortuary by unbalanced Neil Corrigan, who appears to have planned the massacre with Jason - who chickened out and killed himself - and then framed Scott. Ultimately video evidence reveals what actually happened, as well as locating the bomb.