Showing When the Bough Breaks by Jonathan Kellerman

Seven-year-old Melody Quinn is the only witness of a horrific double murder but she can't or won't talk about what she saw. Child psychologist Alex Delaware is brought in to try and get through to her and to the truth of what happened that night. But it soon becomes clear that Melody isn't just traumatised by the murders. Alex is only too aware that LA is a city which spawns ugliness. But is he prepared for the seemingly bottomless pit of perversion and violence that he's about to uncover?