Renee Ballard is an LAPD officer who has been placed in charge of the previously mothballed Open-Unsolved Unit, which at the time had only volunteers working there. Renee starts many days early to allow some time to catch the waves at the beach, but her car is broken into, and she loses her badge, gun, and ID.
She wants to find the thief on her own to avoid letting it become ammunition for those in her department who want to end her career. This leads her to seek advice from semi-retired Harry Bosch.
At about the same time, Renee has taken on Maddie Bosch, Harry’s daughter, one day a week in the Open-Unsolve Unit as a volunteer. Maddie has some interest in a high-profile unsolved case and quickly goes to work; the department has a possible connection to a two-decade-old case of the Pillowcase Rapist who has a genetic link to a man recently arrested.
Ballard is a character in Michael Connelly's book series who often appears alongside Harry Bosch to investigate cold cases.