Julia, a woman suffering from a degenerative eye disease, finds her blind twin sister Sara hanged in the basement of her house. Julia decides to investigate what she feels is a murder case, entering a dark world that seems to hide a mysterious presence. As Julia begins to uncover the terrifying truth about her sister's death, her sight deteriorates, until a series of unexplained deaths and disappearances cross her path. The film stars Belén Rueda and Lluis Homar.