The Blue Hour by T. Jefferson Parker

The plot may sound familiar, but surehanded thriller writer Parker (Where Serpents Dance) proves ever-surprising in his latest novel, the story of an unusual pair of police protagonists and a serial killer stalking beautiful women in California's Laguna County. Tim Hess is a retired cop, fighting lung cancer, who's called back to active duty to find the diabolical killer who "signs" his murders by eviscerating his victims. His boss and partner in the investigation is an attractive, brusque detective named Merci Rayborn, who quickly dismisses the lone suspect in the case, a paroled, chemically castrated Romanian rapist living under virtual house arrest in an apartment complex near the latest crime scene.