A group of young people begin an investigative documentary about a series of disappearances in the Curitiba region. Reports point to the involvement of a supposed "slender man," and the mystery deepens when, upon leaving the city, they find themselves lost and isolated in a region called Serra Madrugada. Intrigue, accusations, and fights are just the first obstacles faced by the group on the most terrifying night of their lives. They are not alone.