The Murder Code — Steve Mosby

Detective Inspector Andrew Hicks thinks he knows all about murder. However horrific the act, the reasons behind a crime are usually easy to explain. So when a woman is found bludgeoned to death, he suspects a crime of passion and attention focuses on her possessive ex-husband. But when a second body is found, similarly beaten, Hicks is forced to think again.

When more murders arrive in quick succession, Hicks realizes he is dealing with a type of killer he has never faced before, one who fits nowhere within his logic. Then the letters begin to arrive....

As the death toll rises, Hicks must face not only a killer obsessed with randomness and chaos, but also a secret in his own past. If he is to stop the killings, he must confront the truth about himself.