Used book – The Last Coyote, Michael Connelly

Following a serious altercation with his superior, Detective Harry Bosch is placed on involuntary leave and ordered to consult a psychologist to control his aggression: his reinstatement into the Los Angeles Police Department depends on it. Harry Bosch initially refuses treatment, then reveals to Dr. Hinojos the secret that haunts him: his mother, Marjorie Lowe, a prostitute, was killed just as she was about to take him out of the center where he had been placed as a young child after being separated from her. And, the crux of the problem, the police investigation that could have helped him accept the reality of this murder was never solved.

Freed by this confession, Harry Bosch then understands that, despite the prohibition against investigating, he must find the person who stole his mother's love from him, and he reopens the case.