The police investigate an apparent break-in that results in the death of Derek Irons, his wife and youngest daughter. Two older children survived the attack but one is in serious condition and in a coma. Irons was a ruthless businessman who targeted his rivals' customers resulting in regular confrontations. Irons was stabbed but his wife and daughter were shot. Sam is reunited with an old friend from Northern Ireland, Det. Supt. Tony Ashton who is the senior investigative officer on the case. Harry assists the police with the death of an old woman who is believed to have fallen down a staircase. His post-mortem reveals evidence that is not consistent with a fall.

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.