From producer Guillermo del Toro (Pan's Labyrinth, The Orphanage) comes a tale of dread and terror from the darkest corners of reality. Julia, a woman suffering from a degenerative sight disease, finds her twin sister Sara hanged in the basement of her house. Everything points to suicide, but Julia is compelled to investigate what she intuitively feels is a murder case. Determined to retrace her sister's final steps, she is drawn into a maze of hidden threats and spiraling dread - a dark world that seems to hide a mysterious, malevolent presence. As Julia begins to uncover clues to the truth of her sister's death, those close to her begin to disappear. Her sight gone and confined to her sister's house, Julia soon finds herself trapped in a nightmare from which she cannot awake.