The police may have a serial killer on their hands when they locate a second body in a site where the first victim was found several months before. The body was trussed up in the same way and had an identical burn mark on his back. There is no apparent link between the first victim, student Michael Haughty, and the second Jason Villers, a probationer at the police college. While the police find evidence that may solve the Otty case, they have nothing on the Villers murder. In a separate case, Harry is approached by the wife of an old university friend who asks him to perform a post-mortem on her husband who died in a fall. Harry finds that his old friend was injecting himself regularly. Leo's family is visiting for a few days but he's constantly being called into work.

When a second police probationer dies at the police college, Sam concludes that they may be dealing with a copycat murder rather than a serial killer. The investigating officer thinks that a fellow probationer may have been responsible for the original murder but the college's commandant, whose son is a student there and soon to be a police constable, would like the reputation of the college protected and the whole thing swept under the carpet. Harry learns that his late friend's wife was prescribing the drugs he was taking and is not quite sure what to do with the information. Leo's relationship with his wife and daughter is stretched thin when he spends most of his time at work and they are left on their own.

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.