In a small town in Massachusetts, four friends named Wren (Joey King), Hallie (Julia Goldani Telles), Chloe (Jaz Sinclair) and Katie (Annalise Basso) invoke the famous Slender Man (Javier Botet). A week later, Katie disappears without a trace, and the other three girls go to her home to try to find some clues about her disappearance. The three girls discover that their girlfriend Kate was involved in the occult area and that she wanted the Slender Man to take her.
At that moment, the girls decide to get in touch with this Slender Man in an attempt to bring back Katie, offering something else in return for her release. Wren, who has deepened this subject of Slender Man and knows mythology very well, warns Hallie and Chloe that they do not have to open their eyes no matter what they would do when they get in touch with Slender Man to avoid death or madness .
However, Chloe panics during the ceremony and opens his eyes, seeing the Slander Man. Sometime later, Slender Man enters Chloe’s house and takes her to the brink of madness. Hallie tells her boyfriend Tom (Alex Fitzalan) that she has seen a certain shooting and asks him not to look at it. Wren, suffering from some frightening visions, is looking for a solution to this problem while Hallie tries unsuccessfully to see his life further. Shortly after, Hallie’s sister Lizzie (Taylor Richardson) suffers a powerful panic attack and is taken to the hospital.