A mysterious doorway leads to a labyrinthine realm of twisting corridors and impossible secrets in this atmospheric thriller.

At the back of a furniture showroom, store manager Clark (Ejiofor, 12 Years a Slave) discovers a mysterious doorway that leads to a labyrinthine realm of twisting corridors and impossible secrets. In an attempt to prove the existence of this new dimension to sceptical therapist Dr Kilne (Reinsve, Sentimental Value), he becomes obsessed with mapping its walls, videotaping its mysteries, and understanding the terrifying entities that haunt its liminal halls. A tense, atmospheric thriller based on the internet phenomenon.