Labyrinth — Bill Pronzini

A young woman's body is discovered near a deserted highway -- with the Nameless Detective's calling card in her purse. Nameless is puzzled. He wonders where she got his card. He also wonders where his next job is coming from. So when a well-to-do woman from affluent Sea Cliff hires him to protect her troublesome brother for a hefty fee, Nameless becomes one happy bodyguard.

The job seems easy enough -- until the man he is guarding becomes the prime suspect in a murder case. Even Nameless couldn't have guessed that these first two murders are related. Soon he is following a grisly trail of corpses, investigating a conspiracy, and fighting for his own life in the icy waters of the Pacific!