Mindhunter, Netflix’s newest crime series, follows a duo of FBI agents as they study the methods and motivations of serial killers in the 1970s. But this is no Mulder and Scully’s X-Files; the show is based on the real-life experiences of John Douglas, a special agent who pioneered the practice of psychological profiling during his 25 years with the FBI.

Douglas recounted his experiences studying and interviewing the likes of Ted Bundy, Ed Gein, and Charles Manson in the book Mind Hunter: Inside the FBI’s Elite Serial Crime Unit, which he co-wrote with the fiction author Mark Olshaker. As you’ve probably already guessed, the book is the inspiration behind the show, which was produced by Charlize Theron and David Fincher for Netflix. Having directed Seven and Zodiac, Fincher is certainly no stranger to the serial killer narrative, and who can forget Theron’s depiction of Aileen Wuornos in Monster.

Over nearly three decades in the FBI trenches, Douglas was responsible for shaping the landscape of criminal psychology. He developed the idea of creating ”profiles” of killers, based on their habits and other contributing factors, in order to predict their next move. The character of Agent Jack Crawford in The Silence of the Lambs is based on Douglas.

Mark Olshaker and the real Holden Ford: John Douglas.

Since leaving the FBI, Douglas has been consulted on a number of major criminal cases. He was a key member of the defense team that obtained the release of the West Memphis Three. His analysis of the Meredith Kercher murder also concluded that Amanda Knox and Raffaele Sollecito were innocent.

Mindhunter will take us to a time way before Amanda Knox or even the West Memphis Three, to when the FBI was just beginning to grapple with the concept of serial killers, and Robert Douglas asked a simple question: why do they do it?

Mindhunter premieres on Netflix on October 13.