Wolf in the Shadows is another in Marcia Muller's Sharon McCone series, and McCone gets better which each subsequent book.
Sharon McCone is a PI living in San Francisco and working for a law firm called All Souls Legal Cooperative. At the beginning of Wolf in the Shadows, McCone is faced with two major issues. First, her job at All Souls is being turned into a supervisor/desk position, something that McCone knows will not work for her. Just when she has to make a decision about her job, her lover, Hy Ripinsky goes missing. Ripinsky is an environmental activist who has a shady past (maybe CIA?). When McCone starts investigating, she discovers that Ripinsky took on a job for an international security agency, RKI. The CEO of a biotech company was kidnapped, and Ripinsky was given the job of delivering the ransom money in exchange for the CEO. But now Ripinsky is missing also, and RKI wants both Ripinsky and their money. They suspect that Ripinsky has skipped town with the ransom money and they hire McCone to find out what happened to him.
McCone travels to San Diego and Mexico on Ripinsky's trail. In the process, she has to deal with illegal aliens, environmental terrorists, crooked Mexican politicians and gang members as well as the ruthless men from RKI. She also must make some hard decisions about what she wants for her future (that's providing she lives to see it through).
The only thing that really spoiled Wolf in the Shadows is that I have not been reading these books in order. Having read one that was published after Wolf in the Shadows, I had a basic idea of how it would end. So from now on, I will be a little more careful to read them in order. Other than that, Wolf is a fine book in a good series.