In 2018, police announced that they had finally arrested the "Golden State Killer," a man responsible for over 140 burglaries, fifty rapes, and at least thirteen murders committed in California throughout the 1970s and '80s. That man turned out to be a former California police officer, Joseph James DeAngelo Jr.

Just two months earlier, the publication of I'll Be Gone in the Dark by Michelle McNamara had rocked the world of true crime. Published two years after her death, the book charts McNamara's obsessive search for the prolific criminal who had been known over the years as the East Area Rapist, the Original Night Stalker, and the Visalia Ransacker, among other epithets. McNamara is credited with coining the "Golden State Killer" moniker and heightening public awareness of the—at the time—still unsolved case.

William Thorp dives into the investigation, exploring the dark side of sunny California, the advances in forensic innovation that made solving this case possible, and the story inside the story—one of an amateur sleuth who dedicated the last years of her life to understanding how one of the country's worst criminals could have spent so many decades undetected.