Julia (wonderfully played by Belén Rueda) cannot believe that her twin sister, Sara, who is blind, committed suicide by hanging. She believes there is someone else in that room when Sara is dying. No one believes her, so Julia tries to investigate herself, sometimes helped by her husband Isaac. The problem is, like Sara, Julia suffers neurodegenerative disease and is going blind.
The movie is presented in pale colour and we often can't see faces of the people. Pictures are often out of focus. This is to make us understand what is Julia going through. The story reminds me to Patrick Süskind's Perfume. If the baddie in Perfume doesn't have smell, this one doesn't have light. He always becomes a shadow that people don't realize his presence.