LAPD Detective Renee Ballard and Harry Bosch come together again on the murder case that obsessed Bosch's mentor - but was this flame kept alive, or a secret that was meant to be snuffed out? Back when Harry Bosch was just a rookie homicide detective, he had an inspiring mentor who taught him to take the work personally and light the fire of relentlessness for every case. Now that mentor, J.J. Thompson, is dead, but after his funeral his widow hands Bosch a murder book that Thompson took with him when he left the LAPD 20 years before - the unsolved killing of a troubled young man in an alley used for drug deals. Bosch brings the murder book to Renee Ballard and asks her to help him find what about the case lit Thompson's fire all those years ago. That will be their starting point. The bond between Bosch and Ballard tightens as they become a formidable investigation team. And they soon arrive at a worrying question: Did Thompson steal the murder book to work the case in retirement, or to make sure it never got solved?
Six months ago, Harry Bosch left the LAPD before they could fire him, and then hired maverick Defense Attorney Mickey Haller to sue the department for forcing him out. Although it wasn't the way he wanted to go, Harry has to admit that being out of the game has its benefits. Until Mickey asks him to help on one of his cases, and suddenly Harry is back where he belongs, right in the centre of a particularly puzzling murder mystery. The difference is, this time Harry is working for the defense, aiming to prevent the accused, Da'Quan Foster, from being convicted. And not only does the prosecution seem to have a cast-iron case, but having crossed over to 'the dark side' as his former colleagues would put it, Harry is in danger of betraying the very principles he's lived by his whole career.