Although you might not have heard of him, you've probably seen or read something about Slenderman in the past few years. Created on a chat forum during a Photoshop competition (no, really), Slenderman has since become a phenomenon and people even believe it to be real - sometimes with tragic consequences. In 2014, two twelve-year old girls allegedly attacked and stabbed a classmate nineteen times with a knife. The classmate luckily survived, however both girls are now in custody awaiting trial. The two girls claimed that the Slenderman made them do it or he'd kill their families.

This documentary by HBO, covers the origins of the Slenderman mythos, the events leading up to the attempted murder and how it was that two young girls became obsessed and infatuated with an internet forum. Shot over 18 months, the documentary follows the ongoing investigation, speaks with the parents of the two girls and discusses what happens when impressionable children find their way into the darkest corners of the internet.