The Overlook reunites Bosch with his most recent former flame, FBI agent Rachel Walling. Bosch must break in a new and much younger partner, Ignacio "Iggy" Ferras, when they're called to take over the investigation of the execution-style murder of medical physicist Stanley Kent on a Mulholland Drive overlook. When a special FBI unit, headed by Walling, arrives and tries to usurp his case, claiming it's a matter of national security, Bosch refuses to back down. Walling's focus on the theft of radioactive cesium from a hospital where Kent assisted in cancer treatments, and her unwillingness to share information only makes Bosch more determined to solve the case.