On the surface Dennis Rader seemed like a "regular guy," but what lied beneath was a sinister fantasy life he enacted under the guise of his alter ego, BTK, while terrorizing Wichita, Kansas. Professor of forensic psychology, Dr. Katherine Ramsland, has been communicating with the serial killer for over 10 years and reveals the motivations behind his gruesome crime spree in this four-part A&E limited series.