CrossFire - Lives, #3

DI David Snow has a serial killer to catch, a killer as mysterious as the crimes he commits. Snow is due to retire, but not before he discovers why someone killed his sergeant and is now coming after him. The killer seems to have a personal vendetta against Snow, but he is determined that no one else should die because of him. His efforts are hampered by the arrival of a new sergeant, 'ruthless' Ruth Winton, for she is not what she seems.
Alarm bells start to ring when Snow realises she is after more than just his job.