Robert B. Parker's Someone to watch over me

Ten years ago, Spenser helped a teenage girl named Mattie Sullivan find her mother's killer and take down an infamous Southie crime boss. Now Mattie is a college student with a side job working for the iconic private eye, and she dreams of being an investigator herself. When Mattie's childhood friend from the South Boston housing projects, Chloe Turner, is found dead, she decides to take on the case. Soon Spenser and Mattie find ties between Turner and dozens of other girls from poor families to an eccentric billionaire with a massive home along Commonwealth Avenue. The man owns properties and businesses throughout Massachusetts with connections to local politicians, the state house, and beyond. Mattie unravels a massive sex-trafficking ring that will take them from Boston to the Bahamas. -- adapted from jacket