Julia and Sara (Belen Rueda) are twin sisters. The beautiful sisters suffer from functional degeneration in their prime. One year ago, Sara was completely blind, and Julia's eyesight was also gradually declining. On a dark night, Sara hanged herself. Julia felt uneasy because of her own sense of the dark. The next day, she and her husband Isaac (Lluis Homar) drove to her sister's residence, waiting for them with incredible bad news. However, all signs indicate that Sara did not seem to commit suicide. She seemed to be accompanied by a mysterious man in her last period of life. Julia tried to follow these clues. Her behavior made Isaac very anxious, and all kinds of panic also accelerated her vision. At the moment when darkness was about to fall, Julia also vaguely sensed that a man who came and went without a trace was always lingering beside her...