EXCLUSIVE: HBO Documentary Films has given the green light to a docuseries based on Michelle McNamara’s bestselling true-crime book I’ll Be Gone in the Dark: One Woman’s Obsessive Search for the Golden State Killer, and production is underway. Oscar nominee and Emmy winner Liz Garbus (HBO’s Nothing Left Unsaid: Gloria Vanderbilt & Anderson Cooper; What Happened, Miss Simone?) is directing.

Courtesy of HBO

It has been a pretty quick turnaround for the project, with production starting less than a month after HBO Documentary Films announced the acquisition of rights to the tome. McNamara’s book was thrust into the spotlight by the April 24 arrest of former police officer Joseph James DeAngelo, who was identified through DNA evidence as the notorious serial killer and charged with a number of the crimes. The big breakthrough in the cold case, subject of McNamara’s book, made the documentary very timely.

McNamara was determined to find the violent psychopath she dubbed “The Golden State Killer,” who terrorized California in the late ‘70s and early ‘80s, committing 50 home-invasion sexual assaults and ten murders. He then disappeared for more than three decades, eluding multiple police forces and some of the best detectives in the area until his arrest last week by the Sacramento Sheriff’s Office.

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I’ll Be Gone in the Dark is comprehensive exploration of the case of an elusive, violent predator by McNamara, the late wife of Patton Oswalt, was in the midst of writing the book when she unexpectedly died in her sleep in 2016. It is also a haunting personal memoir and self-examination of McNamara’s obsessive quest for justice on behalf of the victims and survivors of the crimes. The book was completed by McNamara’s lead researcher Paul Haynes and a close colleague, Billy Jensen, and framed by an introduction by Gillian Flynn and afterword by Oswalt, who also executive produces the docuseries.

While McNamara’s work was not directly credited by by the police for DeAngelo’s arrest, the arrest came less than two months after her book was published, debuting at #1 on the New York Times, and brought attention to the long-dormant case.

Oswalt reacted to the news of the arrest, expressing his desire to get to visit DeAngelo in prison “not to gloat or gawk — to ask him the questions that (McNamara) wanted answered in her “Letter To An Old Man” at the end of I’ll Be Gone In the Dark“.

Oswalt and the Estate of Michelle McNamara are repped by UTA and attorney Lev Ginsburg.