In Springdale, Washington, a teenage girl taking pictures of herself is killed in her own bedroom by what appears to be Thinman (a pastiche of Slender Man), some kind of monster that appears in various videos and pictures of unnatural deaths. Sam and Dean find their old ghost hunting rivals Ed and Harry of the Ghostfacers are also there investigating, collecting more stories on Thinman. Sam and Dean are confused because the deaths don't seem related to the supernatural and the pictures seem faked, but then Thinman is caught on-camera murdering a diner manager. After Harry himself narrowly escapes Thinman, Ed confesses that he had invented Thinman to keep Harry from leaving to lead a normal life as their old teammates had, a revelation that infuriates the other man. Sam and Dean are taken captive by the local deputy, who reveals that he and his psychopathic partner-in-crime, a busboy who had killed his boss the diner manager and the girl for petty reasons, have been using Thinman as a cover to go on a killing spree, disguising themselves as Thinman and staging the murders as supernatural occurrences to make it seem that Thinman is real in order to feed the legend. They plan to have "Thinman" kill Sam and Dean next, but when Ed and Harry arrive, they get distracted, allowing Sam and Dean to break free and fight back; in the ensuing struggle, Dean kills the busboy and Harry is forced to kill the deputy to save Ed. Dean then covers up their involvement by staging the scene so it looks like the killers killed each other. At the end of the episode, Harry refuses to forgive Ed for his deception and leaves the Ghostfacers and Ed behind for good.
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