For longtime Connelly readers: this is cover-billed as a "Ballard and Bosch" novel. More accurately, it's a "Ballard, Bosch, and also another Bosch" novel. It's mostly Renée Ballard. Harry Bosch does make some critical appearances. But I think his daughter Maddie actually shows up on more pages.
There are multiple plot threads. First, Ballard returns from her morning surfing to find that her car's been burgled, with the perpetrator stealing her wallet, cop badge, and gun. This is terrible news, because she has enemies in the department just waiting for her to make a mistake like this, using it to stymie her career. So she has to solve this on her own… or maybe call in some assistance from an ex-cop who had similar battles in the past! And it's not long before her off-the-books investigation leads to much more serious criminality.
Second thread: Renée heads up the LAPD's "Open-Unsolved Unit", tasked with using new investigative techniques on crimes that stumped previous investigators. And they have discovered a DNA link to the "Pillowcase Rapist", who had a reign of terror over LA a couple decades back. That link turns … complicated, uncovering a lot of scandalous and unsavory behavior in Pasadena.
And one plot thread doesn't start up until page 147 or so, and I won't spoil it. But it's a biggie.
One cute thing when Renée is searching through a storage locker, and finds a book collection containing "several authors she recognized, including some she had even read: Child, Coben, Carson, Burke, Crumley, Grafton, Koryta, Goldberg, Wambaugh,…"
Notice anyone conspicuous by their absence? Yes, I guess in the parallel universe where Ballard and the Bosches exist, Michael Connelly cannot.
(For Tom Petty fans: yes, it's the hardest part. Says so on page 142.)