Detective Harry Bosch learns the DA's office is examining new evidence which threatens to overturn an old case, potentially jeopardizing all of Bosch's other convictions. Meanwhile, a robbery turned murder at a local pharmacy exposes an opioid ring that drags Bosch down a dangerous path.

Bosch and Edgar uncover more details about the pharmacy murder and the opioid operation, while Detective Robertson works a tandem homicide. As Bosch pushes back against the deathbed confession at the heart of Borders' petition for release, he enlists the help of a longtime adversary. J. Edgar tries to persuade a former CI to cooperate with an investigation.

As Bosch digs into the Skyler case, he becomes more convinced that the Olmer confession is false. Robertson zeroes in on the identity of the pharmacy killers. Seeking a connection to the pill mill, Bosch goes undercover and befriends a fellow vet. Pierce and Vega work a lead on Jose, Jr. Edgar discovers that Gary Wise's life was more troubled than it appeared.

Bosch continues his hunt for the pharmacy killers. Edgar confronts possible suspects in Gary Wise's murder. Hoping to rattle some cages, Bosch pays a surprise visit to an old nemesis. Chief Irving considers a run for mayor.

Bonner has a breakthrough in the Borders case. Christina Henry gets closer to uncovering police misconduct. Bosch realizes not everything with the Borders investigation was as it appeared. Edgar and Bosch get more than they bargained for in a return trip to the Garcia Clinic.

Stranded in the desert without backup, Bosch closes in on his murder suspects and learns more about Clayton. Worried about her dad, Maddie turns to Billets for answers. Billets, in turn, confronts Edgar about Bosch's rogue mission. Pierce and Vega head to Bakersfield to find Jose Jr. Anderson gets a tip about police misconduct in the Borders case, and Cronyn implicates Bosch.

Edgar interviews Clayton, desperate for details on Bosch's location in the desert. Meanwhile, Stones and Carter tell Bosch he's going home, but ominously take him up in the plane by himself. Billets resolves to turn a blind eye to the falsified crime stats. Crate plans Barrel's surprise retirement party. Irving makes his case to the DA, and Edgar gets closer to finding Bo Jonas.

Chandler and Bosch locate Spencer, and try to pressure him to flip. At Borders' habeas hearing, Chandler gains standing for Bosch and reveals the Cronyns' conspiracy. Edgar connects Marcos and Arias to a shady Haitian under CIA protection. Irving considers his future. Pierce and Vega catch a gruesome new homicide. Bosch has one remaining loose end to tie up in the Skyler murder.

Pierce and Vega find more body parts, and tie their murder to an ongoing RHD case. Maddie tells Bosch she sent the memo to Chandler, and doesn't regret it. Edgar knows who killed Gary Wise, but can't prove it. At his retirement party, Barrel springs his own surprise. Bosch commits to solving the murder of Daisy Clayton, Irving makes a big announcement, and Walsh returns for one last dance.