Dead Aim — Thomas Perry

Robert Mallon has lived for ten quiet years in affluent Santa Barbara, California, when an encounter on a beach with a mysterious young woman shatters his peaceful, carefully constructed life. Despite Mallon's desperate attempts, he loses her, and becomes obsessed with discovering why. He hires detective Lydia Marks to uncover the secrets of this stranger's life, and what they learn propels them into a terrifying world of sinister secrets and deadly hatreds. Targeting Mallon is the master hunter Parish, a man with an expert understanding of evil, who preys on rich people's desires for dominance and revenge. Mallon is drawn into a lethal struggle with this deadly adversary--and then another, and another, and another.