Five years ago, nurse Chen Nian mysteriously "fell off a cliff" in the Qingshan Sanatorium in the mountains, which became a lingering obsession for his brother Chen Yimei. Until a string of strange coordinates and a text message "Save me, run" came, he resolutely broke into the abandoned sanatorium blocked by thick fog, but stepped into a carefully woven horror trap. Behind the rusty iron door, there are twisted smiling graffiti, messy and strange footprints, and a diary with a handwriting that changes from neat to crazy, gradually uncovering the conspiracy of the mad doctor Wang Jingming's immortality experiment - those "monsters" who have been genetically modified and lost their human form, and the bloody secrets hidden behind the red door of the basement, all point to the truth about the disappearance of his sister.
