Seo-jin (SHIN Min-A), a renowned photographer, is shattered by the sudden and mysterious death of her twin sister and sets out to uncover the truth. As her investigation deepens, an unseen presence begins to close in, twisting reality and driving her into a spiral of paranoia as her vision fades away. Now trapped in encroaching darkness, Seo-jin faces a terrifying revelation that shatters everything she thought she knew.