Beware the Slenderman
HBO's documentary following the true story of two girls that brutally stabbed a another girl twelve times in Waukesha, Wisconsin claiming the Slenderman influenced them to do it. The investigation took over 18 months and features interviews with the parents of the two attackers.
Slenderman (Slender Man) is an entirely fictional character that began as an Internet meme by the Something Awful community in 2009. It became the 'star' of its own series of video games and has since been popularised elsewhere in pop culture.