Showing There's Something in a Sunday by Marcia Muller

It's a cold Sunday in San Francisco. Sharon McCone's alone on a routine surveillance job, following a man named Frank Wilkonson through the city's lush horticultural hot spots to the serene foothills of the Diablos. But when she returns to find her kindly old client in a pool of blood, nothing she's learned explains it. The search for answers takes her from Wilkonson's sullen brood on Burning Oak Ranch, to the eccentric havoc of a household in the Haight, to Golden Gate Park and the desperate digs of the homeless. Unraveling the threads that link a homeless man, a pair of prominent activists, a wayward rancher, and a mysterious missing beauty, Sharon is plunged into the depths of domestic mayhem... entering a realm where dreams shatter and marriage leads to bloody murder.