Dark Lady by Richard North Patterson

The setting is Steelton, a struggling Midwestern town trying to save its decaying inner city by building a major league baseball stadium. Dark Lady introduces Assistant County Prosecutor Stella Marz, who has escaped her alcoholic father and working class background to become head of the Prosecutor's homicide unit. Her ambition is to become County Prosecutor. But this ambition, indeed her very survival, is threatened when her ex-lover Jack Kovak, a drug lawyer, is murdered, and Stella leads the investigation. There are more deaths and revelations about Jack Kovak's dealings with the city's crime lord, and a trail of wrong-doing, that implicates officers in law enforcement, possibly within her own office. As her inquiry draws her into a re-examination of her own complex past, her certainty that she is being watched and followed, leads her to fear for her own future.