A serial killer suffers from Antisocial Personality Disorder and appears normal or charming, sometimes referred to as the "Mask of Sanity." Sometimes there is a sexual element to the murders and they may have a commonality such as gender, occupation, appearances, race, etc. The term serial killer was coined in the 1970s due to cases such as Ted Bundy and David Berkowitz. According to an FBI Behavioral Unit study 85% of the world's serial killers are in America. At any given time 20 - 50 unidentified active serial killers are at work continually changing their targets and methods. "Hidden Evil" is a fictional story of one of them.