Retired detective Paul Holes has never read his friend Michelle McNamara’s New York Times-bestselling book I’ll Be Gone in the Dark, about the hunt for the Golden State Killer — despite factoring heavily into its contents. First, he was too busy tracking down the man he and McNamara had teamed up to find. Then it was just too hard — she died before the book could be finished, before the killer could be found.

“I’m looking at the book right now sitting on my bookshelf, and I just can’t get the emotional courage to open that book and start reading it,” Holes tells Rolling Stone. “When she died, I lost somebody in my family. I can still hear her voice in my head.”

Holes feels the same way about the new six-part HBO docuseries (premiering Sunday) that shares the book’s name — although he appears in several episodes, he’s not sure he’ll ever want to watch it. The comedian Patton Oswalt, who was married to McNamara before her death at age 46 in 2016, can only make it through four episodes himself. And that’s not just because the subject matter is so hard; it’s because I’ll Be Gone in the Dark is imbued with its writer’s spirit. “It was like, ‘Oh, there she is,’” Oswalt tells Rolling Stone. “After a while, it just got too hard for me to watch.”

McNamara had long been engrossed by darkness — ever since her neighbor Kathleen Lombardo was murdered just a few blocks from her home in Oak Park, Illinois, in 1984, when McNamara was 14. She became obsessed as an adult, however, with a shadowy figure she dubbed the Golden State Killer — a then largely unknown serial killer/rapist who is suspected of committing at least 12 murders, 50 rapes, and 100 burglaries in California between 1974 and 1986. His other names include East Area Rapist, the Original Night Stalker, and the Visalia Ransacker.

In 2006, McNamara launched a website titled True Crime Diary dedicated to stalking him and other fiends, going on to write articles for Los Angeles Magazine in 2013 and 2014 about the GSK. Those pieces earned her a book deal — and a ticket to deeper fixation. She rode along with Holes when he was still an active detective in California’s Contra Costa County; he’d been on the trail of the GSK since the Nineties. Holes was at first standoffish, since he didn’t want to get reprimanded for consorting with the press, but they became friends as McNamara’s involvement in the case grew. “She was an investigator at heart,” he says. “Even without any type of experience or training, she just seemed to have a knack.”

McNamara also teamed up with fellow internet sleuth Paul Haynes, whom everyone online called “The Kid,”  to sort through towers of file boxes about the GSK — swapping theories and chasing leads that often went cold. “Weird obsessions — like being fixated on a decades-cold serial murder case that never personally touched you — can make one feel uneasy and alone,” Haynes tells Rolling Stone. “Connecting with someone like Michelle who shares your obsession and thinks about it in the same way is validating. Suddenly, you’re no longer operating in a vacuum, but symbiotically, in a partnership.”

Still, the story of the notorious killer consumed McNamara, sometimes for the worse. She leaned on prescription drugs at times to sleep and to concentrate when tensions over the book and subject matter were too much. “I knew that there was an obsessive aspect to what she was doing,” Holes says. “I really wasn’t thinking that she was having any type of trauma as a result of what she was doing on the case. That may have been a massive oversight.”

The subtitle of her 2018 book, then, is starkly apt: One Woman’s Obsessive Search for the Golden State Killer. A mix of memoir and true crime, it showcases not only the demon that was the GSK — but the demons he stirred within McNamara. She died of an accidental overdose in 2016 without finishing the book; Haynes and crime writer Billy Jensen stepped in at Oswalt’s behest to tie it all together to achieve his wife’s dream. And so powerful was the book that HBO acquired the rights before publication and started work on a series based on it, enlisting the veteran documentary director Liz Garbus to helm the six-part show.

Garbus never met McNamara but was drawn in by her all the same. “I was just blown away by her voice,” she tells Rolling Stone. “I identify so much with Michelle. We were the same age,” she elaborated in a release. “I empathized with her.” Garbus, who’s been nominated for two Oscars (for the 1998 prison doc The Farm: Angola, USA, and 2016’s Nina Simone biopic What Happened, Miss Simone?), is no stranger to true crime. She recently directed the Netflix film Lost Girls, a crime drama centered on the real-life Long Island serial killer and starring Amy Ryan, who also provides voiceover for some of McNamara’s writings in I’ll Be Gone in the Dark.

Oswalt shared with Garbus countless artifacts and writings from his wife — from photos of her as the large-eyed youngest child of a massive family, to footage of her goofing off in high school, to video of McNamara wrangling her baby, Alice, as she talks about the GSK. “My role [in making the series] was the same as my role when the book was being completed,” Oswalt says. “I handed over materials to professionals who knew how to shape it and tell the story. I contacted all of her family members, all of her friends, went through all of my stuff. I handed over both of Michelle’s laptops, her phone, iPad. Basically put the material in the hands of somebody that I knew could do right by it.”

Armed with McNamara’s physical memories, Garbus made her film into a visual representation of McNamara’s book, which merged her hunt for a killer with her life as a mother and wife. McNamara is all over the doc — a story about how she initially bonded with Oswalt over 1954 classic The Creature From the Black Lagoon becomes a visual motif via old black-and-white movie footage, a stand-in for the GSK, who hunts his victims via the waterways of California. Her diary entries and articles serve as voiceovers. Her office is recreated painstakingly — complete with a pinboard crowded with both clues about the GSK and her child’s art. Most strikingly, however, her empathy for and close relationships with the GSK’s rape survivors — along with Garbus’ expert filmmaking — put the film’s emphasis not so much on the monster but on the humanity he tried (and failed) to strip away.

“We approached [the film] from her point of view,” Garbus says. “I think that the focal point is what happened to all of these incredible survivors during this period in which the Golden State Killer was active — and Michelle’s drive to crack the case.” The docuseries showcases McNamara’s deft handling of rough subject matter — as she interviews one survivor, she commiserates with the woman about her relationship with her mother, letting slip that her own mom used to slide notes under her door when she was angry instead of openly discussing their issues. Garbus’ doc echoes McNamara’s respect for these traumatized women. “Some of them were folks who hadn’t spoken before,” Garbus says of the women who appear in the show. “I think they knew we were going to take this case very seriously. And we had the approach that Michelle had, which was very survivor-oriented.”

“She was very easygoing,” Holes recalls of McNamara’s interview style. “I kind of have the same kind of thing, same skill set — because I was a military brat and constantly having to integrate with new kids as I was growing up, from all the moves. She was able to integrate with different people. And I think that benefited her tremendously.”

“The word that kept surfacing for me while viewing the series was ‘loving,’” Haynes adds. “It’s both a loving tribute to Michelle as well as the definitive motion-picture document of the case, obliterating everything else that’s preceded it. When I talk about Michelle with people, I often hear ‘I wish I could have known her.’ Watch this docuseries, and you’ll know her.”

Viewers will also come to know the survivors. We see them puttering in their gardens, visiting Paris on a hard-won trip, embracing each other at a backyard party after the alleged GSK is caught — which happened, coincidentally, just as the documentary began filming. McNamara’s book came out in February of 2018 — and former cop Joseph James DeAngelo was arrested on April 24, 2018, on the strength of DNA evidence. He is charged with 13 felony counts of murder with special circumstances and 13 counts of kidnapping to commit robbery (related to his sexual assault cases).

“It was literally the first day of filming,” Oswalt says, laughing. “We had done a book reading in Chicago that night, and we all went to bed, and we woke up the next morning and the news was out that he had been captured and arrested. And you see that in the documentary. My reaction. We’re all just like, ‘What? Where do we go from here?’”

As it turned out, DeAngelo’s arrest didn’t change much about the original thrust of the show — the story is not about the now-frail old man in a wheelchair, a specter who has yet to publicly utter a word about the case. His next hearing is June 29th; Garbus and Holes plan to watch, Oswalt does not. “I wanted to approach it as a journey of investigation that Michelle was going on that we would go along with her,” Garbus says. “Of course, once you find out who this person [DeAngelo] is, as a filmmaker it’s irresistible to want to know more. But really, the film is about the survivors and Michelle.”

One of the last parts of the doc was shot first — that book event in Chicago, where survivors and readers mingled with Oswalt and other friends of McNamara. It’s a joyful scene, one that stands in sharp contrast to the dark tales of the GSK’s misdeeds and machinations. Oswalt remembers being overcome by meeting these people — by chatting with the women who had lived in his wife’s head for so many years. Who had, in some cases, become her friends. “It’s overwhelming, but it’s hopeful,” he says of the legacy McNamara left behind. “It means that she’s not really gone.”