Before the FBI's famous Mindhunter program, small-town psychologist, Dr. Al Carlisle was called to assess several prisoners at Utah's State Prison. This was a time before law enforcement had coined the term 'serial killer', so Dr. Carlisle didn't have any idea of the types of people he was meeting. But as he spoke with them he began recording them to help him unearth the darkest secrets of the human mind. After Carlisle’s death in 2018, his family discovered over 650 hours of inmate tapes which forensic experts thought were just rumored to exist. This Peacock True Crime documentary series centers on various inmates, many of whom would become household names:  including Ted Bundy, the HiFi Killers, Arthur Gary Bishop, and Manny Cortez.