Following on from 'Jack-Knifed' and 'The Coopers Field Murder', the author in 'Killing by Colours,' takes Detective Chief Inspector Martin Phelps in search of a serial killer who appears to have something of a personal interest in the DCI.

When the body of the first victim is discovered there are key elements that link her to a poem sent to the DCI's home address. Subsequently the killer teases the team by giving clues to the identity of his victims and to the venues he has arranged for his murders. The location for each brutal stabbing is in some way connected to the colour allocated to each victim by the killer and the newly appointed DC Helen Cook-Watts hits on a possible theory for identifying the sequence of colours.

The murders have been years in the planning and there is no way the victims have been chosen at random. They are people that the killer has known at some point during his life and who he believes he has reason to hate. DCI Phelps is on his hate list but does he want to murder Martin or just ruin his career?

Detective Sergeant Matt Pryor is worried about the safety of his boss. Are his fears warranted? Is Martin on the list of potential victims or is he just a post-box for the killer's bizarre poetry.