The Wrong Side of Goodbye (Harry Bosch #19) by Michael Connelly

Harry Bosch has left the LAPD, but he’s far from done solving cases. Now working as a private investigator, he’s called upon by a dying billionaire with a shocking request: Find the heir he may have fathered decades ago. Meanwhile, Bosch also volunteers for the San Fernando Police Department, chasing down a dangerous predator known as The Screen Cutter. As Bosch balances both cases, he uncovers long-buried secrets—ones that some would kill to keep hidden.