The Trailer for HBO's 'Beware The Slenderman' Will Chill You To Your Bone

A real life horror story.

The Internet can be a terrifying place, especially if you're young and malleable. That idea comes into sharp focus in the chilling new trailer for Beware the Slenderman, HBO's upcoming documentary about the macabre meme Slenderman, and the horrific crime it inspired.

Morgan E. Geyser and Anissa E. Weier were just 12 years old when they stabbed a fellow classmate 19 times in the backwoods of a rural Wisconsin town. And though their victim survived the brutal attack, the case gripped the nation after bizarre details surfaced, and a tall, faceless figure known only as Slenderman became a focal point of the investigation.

In the below clip, the two suspects—who are now 14 but are being tried as adults—confess that they committed the crime as a way of proving that mythological creature was in fact real. Though the documentary will feature footage from their ongoing trial, director Irene Taylor Brodsky insists that it’s not about the quest to convict them. Instead, it will focus on "the court’s deliberation whether the girls should be tried as adults or children," adding that the anguish and honesty of their parents "anchors the film’s narrative to its tragic core."

Beware the Slenderman premieres on HBO on January 23, 2017. Watch the trailer above.