Beware the Slenderman: Watch the Trailer for HBO's Bone-Chilling Documentary

While Slenderman is fictional (we hope), he did inspire a shocking attack in Wisconsin. In 2014, Morgan Geyser and Anissa Weier, both 12 years old at the time, lured their best friend into the woods and stabbed her 19 times; they claimed they did it for Slenderman. The documentary follows the families of the attackers for over 18 months, delving into how and why the girls did what they did.

Oscar-nominated documentarian Irene Taylor Brodsky directed the film. She's behind 2007's Sundance darling Hear and Now, in addition to several other docs. Sophie Harris is her producing partner on the project, and the two have worked on several films together, including the 2015 documentary short Open Your Eyes.

Beware the Slenderman is debuted at the South by Southwest film festival earlier this year, but since it's being distributed by HBO Films, you'll get to enjoy it from the comfort (and relative safety) of your own home on Jan. 23, 2017.