When the Bough Breaks by Jonathan Kellerman

Dr. Morton Handler practiced a strange brand of psychiatry. Among his specialties were fraud, extortion, and sexual manipulation. Handler paid for his sins when he was brutally murdered in his luxurious Pacific Palisades apartment. The police have no leads, but they do have one possible witness: seven-year-old Melody Quinn.

It's psychologist Dr. Alex Delaware's job to try to unlock the terrible secret buried in Melody's memory. But as the sinister shadows in the girl's mind begin to take shape, Alex discovers that the mystery touches a shocking incident in his own past.