When Harry Bosch was eleven years old, his mother was murdered and he became a ward of the state, housed in MacLaren Children's Center, a notorious facility where abuse was rampant. Decades after its closure, a massive class action lawsuit has resulted in a multibillion-dollar settlement for former residents. But when Bosch's half-brother, defense attorney Mickey Haller, brings him word that Harry is entitled to $400,000, Bosch says he doesn't want the money. He wants justice.

News of the settlement awakens his memories of a place he had hoped never to revisit, and a boy named Chops, a fellow inmate who wound up dead. Chops's body was found in a hidden space under a staircase that the staff used to discipline their charges. The kids knew it only as "the hollow." But Chops's death was covered up and never solved. Now Bosch knows he must reopen the investigation and learn the truth, even if the killer is long dead.

As Bosch digs into the files, he picks up the trail of a predator who not only survived, but went on to a life of vicious crime. Forced to face a history that both scarred him and launched him on his mission as a cop, Bosch must bring down a sadistic criminal and finally put to rest the demons of his past.