The cat who went up the creek - Lilian Jackson Braun

Pickax's favorite columnist, James Qwilleran, is enjoying a brief holiday in the nearby town of Black Creek - but his two Siamese, who prefer the spaciousness of their home, beg to differ.
The blissful tranquility is soon interrupted by the discovery of a body floating down the creek.
And a possible motive for his murder is suggested when several gold nuggets are found in his possession.
Might he have been illegally prospecting for gold?
If so, it seems he wasn't the only one in search of an easy fortune.
And his competitor is far more determined to strike it rich...