Show of the week
Beware the Slenderman
He was a golem created in a dark corner of the internet. Part Photoshop gag, part urban myth, Slenderman rode crowdsourced creativity to loom so large in the imaginations of two 12-year-old Wisconsin girls that they apparently were trying to appease him when they stabbed a friend 19 times and left her for dead. This documentary, from award-winning director Irene Taylor Brodsky, plays as a dark fable about how vulnerable young minds can be when the internet supplies a manifestation of their deepest fears, then leaves them to discern fact from fiction. Monday, Jan. 23, at 10 p.m., HBO
• All listings are Eastern Time.