Snuff (Discworld book #39), Terry Pratchett

The Discworld is very much like our own - if our own were to consist of a flat planet balanced on the back of four elephants which stand on the back of a giant turtle, that is . . .

'The jurisdiction of a good man extends to the end of the world.' It is a truth universally acknowledged that a policeman taking a holiday would barely have had time to open his suitcase before he finds his first corpse. Commander Sam Vimes of the Ankh-Morpork City Watch is on holiday in the pleasant and innocent countryside, but not for him a mere body in the wardrobe. There are many, many bodies - and an ancient crime more terrible than murder.

He is out of his jurisdiction, out of his depth, out of bacon sandwiches; and out of his mind. But never out of guile. Where there is a crime there must be a punishment.

They say that in the end all sins are forgiven. Vimes is about to uncover the exception.