Plot
Harry Bosch returns to homicide duty after transferring to the Los Angeles Police Department's Homicide Special squad. Dr. Stanley Kent lies dead at Mulholland Dam, shot twice in the back of the head. Kent's hospital identification badge and radiation-monitoring rings identify him as a medical physicist with access to radioactive caesium. FBI agent Rachel Walling arrives, and Bosch learns that she had visited Kent before his death.
At Kent's home, Bosch and Walling find Alicia Kent tied up. She says two men forced her to surrender her husband's gun, her car keys, and her email password. A ransom message demanded that Kent steal caesium and deliver it to the overlook. At Saint Agatha's clinic, the detectives and federal agents find that Kent removed 32 radioactive capsules from a secure safe. His note says that his wife was being held hostage.
The missing caesium alarms federal authorities, who fear an attack using a dirty bomb. The FBI and the Department of Homeland Security take control of the search, while Bosch insists on pursuing Kent's murder. His young partner, Ignacio Ferras, worries that Bosch's refusal to follow federal direction will damage his own career.
Bosch interviews Jesse Mitford, a young man who witnessed the shooting from nearby. Mitford recalls gunshots, flashes, and several vehicles, including a Porsche. Although he cannot identify the gunman, his account gives Bosch a fresh source of evidence. Bosch also examines Kent's phone records and emails, which help clarify the hours before his death.
Federal officials suspect Ramin Samir, a controversial former professor, and arrange a raid on his home after a vehicle associated with the case is found nearby. Captain Don Hadley supports the operation. Bosch doubts that Samir is responsible, but the raid proceeds, ending in gunfire and Samir's injury. The operation fails to locate the missing radioactive capsules.
Bosch continues examining the Kent household. He notices that a yoga poster has been removed from a wall and later learns that a matching poster was found in a rubbish container holding the missing caesium. He compares the image with the photograph used to support Alicia's account of her captivity. The resemblance leads him to suspect that Alicia staged her own restraint.
Bosch comes to believe that Alicia and FBI agent Clifford Maxwell conspired to kill Kent for financial gain. The apparent terrorist threat served as cover for a domestic murder. Maxwell's access to federal resources helped divert attention from the couple's actions. When Bosch's theory becomes clear, Maxwell kills Alicia and attempts to escape.
Bosch resolves the case, and the missing caesium is recovered. However, exposure to radiation leaves him physically unwell. The case also strains his partnership with Ferras and his dealings with Walling, who must reconsider her earlier doubts about Bosch's judgment.
