In the quiet desert town of Elephant Butte, New Mexico, a nightmare was hidden in plain sight. This week, we dive into the chilling case of David Parker Ray, a man who spent decades and over $100,000 perfecting a soundproofed semi-trailer he called his "Toy Box."

To the world, Ray was a park ranger and a mechanic. Behind closed doors, he was a calculated predator who utilized surgical tools, elaborate pulleys, and a homemade audio tapes to inflict unimaginable suffering. For over 40 years, Ray is suspected of abducting and torturing dozens of women, many of whom were left with induced amnesia or simply never seen again.

For nearly 20 years, Donald Harvey worked in the shadows of hospitals in Kentucky and Ohio. Known as a dedicated nurse's aide, he was actually one of the most prolific serial killers in U.S. history.