Dark Sacred Night by Michael Connelly

Harry Bosch teams up with LAPD Detective Renée Ballard to face the unsolved murder of a runaway, and the fight to bring a killer to justice.Detective Renée Ballard is working the night beat — known in LAPD slang as "the late show" — and returns to Hollywood Station in the early hours to find a stranger rifling through old file cabinets. The intruder is retired detective Harry Bosch, working a cold case that has gotten under his skin.
Ballard can't let him go through department records, but when he leaves, she looks into the case herself and feels a deep tug of empathy and anger. She has never been the kind of cop who leaves the job behind at the end of her shift — and she wants in.
The murder, unsolved, was of fifteen-year-old Daisy Clayton, a runaway on the streets of Hollywood who was brutally killed, her body left in a dumpster like so much trash. Now Ballard joins forces with Bosch to find out what happened to Daisy, and to finally bring her killer to...