Stone Angel by Carol O'Connell

When NYPD detective Louis Markowitz arrested 10-year-old Kathy Mallory for stealing, he and his wife adopted her, rather than taking her to juvenile hall.

Now Markowitz and his wife are both dead, and Mallory has grown from a feral child into a formidable cop, both beautiful and cold.

After solving the mystery of Markowitz's murder, Mallory journeys further back into her past to find out the truth about what happened to her biological mother.