"Who lives next door to you?" asks psychologist and true crime expert Emma Kenny in "The Serial Killer Next Door: Chilling True Stories of the Killers Hidden Among Us" (Mobius).
"Perhaps a friendly postman or a businessman in a sharp suit? These are the faces you recognize, individuals as 'ordinary' as you or me. But it's in the very depths of this ordinariness that a frightening anomaly could lurk.
"For within some of these seemingly normal souls lie desires so dark, they are almost impossible for the majority of us to comprehend."
"The Serial Killer Next Door" revisits the stories of 15 notorious mass murderers, from the more familiar, like Ted Bundy, to others such as Dorothea Puente, who killed nine elderly and disabled residents in her boarding house in Sacramento Calif., and Jerry Brudos, the 'Shoe Fetish Slayer' from Salem, Oreg. "Unravelling the minds of serial killers requires a fortitude to delve into the darkest recesses of human nature," writes Kenny.
From the outset, the book is graphic and distressing in equal measure.
The story of David Parker Ray, the so-called "Toy-Box Killer," is a case in point. A sexual torturer and serial killer suspected of more than 60 murders that began in the 1950s and ended in the late 1990s, Ray kidnapped women before chaining them up in a windowless and soundproofed trailer at his home in Elephant Butte, NM, and subjecting them to unimaginable abuse for months at a time.
Many died, their bodies then filled with cement so he could throw them in the local reservoir or river knowing they would never float to the surface.
Those that survived were "plied with a cocktail of drugs designed to confuse them and create a state of amnesia," writes Kenny. "This would ensure that they would be unable to implicate Ray to the police."
It was only when 22-year-old Cynthia Jaramillo escaped his clutches in 1999 that the full extent of Ray's depravity became known. "His innocuous-looking trailer turned out be a horrifying prison of torture," adds Kenny. "David Parker Ray's story serves as a chilling reminder of the depths to which humanity can sink."
Like all the killers featured in the book, David Parker Ray shared the same apparently normal characteristics that allowed him to hide in plain sight. "Ray was well known within the community as a polite man who had held down a full-time job and was respected as a mechanic. He also had a clean record," adds Kenny.
It's this ordinariness, argues Kenny, that makes their crimes all the more shocking. "How does one make sense of the coexistence of banality and brutality?" she asks.
Take former soldier Israel Keyes, who took his own life in prison while awaiting trial for a series of gruesome murders across the country between 2010 and 2012. He was, writes Kenny, "quiet and introspective . . . The unassuming man who might have waved hello as you fetched your morning paper."
But what these killers also have in common is the power "gained through the infliction of physical and psychological pain and humiliation."
It is also, says Kenny, a means to boost low self-esteem on the one hand and a way to escape or erase the memories of difficult backgrounds, typically involving abuse, violence and "a deep-seated 'fear of rejection' on the other.
It's certainly the case with Aileen Wuornos, who killed seven men and is regarded as America's first female serial killer. Her childhood was dominated by the violent sexual abuse she suffered at the hands of family members and she had tried to commit suicide six times before her killing spree began in 1989.
"Her life was the epitome of a horror story from her conception to her execution by lethal injection on 9 October 2002, when she was just 46years old," writes Kenny.
Indeed, when Wuornos (played by Charlize Theron in the 2003 Oscar-winning movie "Monster") was executed in October 2002, one of the final things she said was: "I deserve to die."
Kenny also reveals how many serial killers don't fit stereotypical notions of what a mass murderer might look like.
Tamara Samsonova, for example, was a "small and fragile" 68-year-old grandmother who, nevertheless, killed her lodger and a woman she later lived with, before dismembering their bodies, eating their lungs, and scattering the remaining pieces in the area around her home the Fruzensky District of St. Petersburg, Russia.
Now 77, Samsonova remains in custody as police investigate a further 14 potential murders, including that of her husband. "Elderly women are rarely perceived as capable of heinous crimes," writes Kenny.
"This underestimation, combined with a lack of overtly suspicious behavior, created a perfect smokescreen."
It's further proof, if it were needed, that you never can tell just what your neighbors might be up to behind closed doors.
By the end of the book, as Kenny concludes, "you may even find yourself watching a little more closely, listening a little more intently, and wondering: Do I really know who lives next door to me?"