The back of the book gives a fuller plot description:
'Seattle Police Sergeant Lou Boldt and psychologist Daphne Matthews have a new enemy on their hands: Fire. Fire so hot and all-consuming that no one can get near to the cause. Temperatures like this can only be caused by an accelerant, but the fuel is as much of a mystery as the identity of the arsonist who sets the flames. Then a Seattle fire marshall reveals to Boldt the ominous quotations sent to him before each of the fires, and a twelve year old boy accidentally witnesses an unusual deal. Can either of them be trusted to reveal the truth?'
I rate this alongside 'No Witnesses' as the best in the Lou Boldt series so far. Each of the series so far has taken a different type of 'crimes against persons' as its focus, and this time arson is at the centre of the investigation. This works well because it takes the homicide team out of their comfort zone as they have to rely on fire investigators in order to understand what happened (distancing the detectives from the crime scene and also the victims) -this unease is compounded by the fire investigators being unsettled and baffled by the ferocity of the fires, which cause not only the victims to be almost vaporised but also the crime scenes. Given that the fires are being set by someone with an expert knowledge of fire, can the fire investigators themselves be above suspicion?
You don't need to have read the previous Boldt / Matthews books to follow what's going on, although past cases and personal histories are referred to and adds the development of the main characters.