To prepare for her role, Jessica Alba took violin lessons for 6 months, which she started while filming 4: Rise of the Silver Surfer (2007). She also learned basic Braille.
Xavier Palud and David Moreau's second feature film and first American film. They were offered the job thanks to the success of their French horror film Ils (2006).
Just like the original Gin gwai (2002), the story takes it source in a real event, that of a young woman who committed suicide shortly after undergoing a cornea transplant, whereas she seemed to be living her perfectly normal and healthy life.
Jessica Alba declared that while she'd been wanting to do a horror thriller for a long time, she didn't want to do a slasher where each character dies in a more outrageous and bloody way, whereas she found this film to be elegant and very well written and her character Sydney to be elaborate and very interesting, thus enabling her to stretch her acting abilities.
While the supernatural elements of the film are pure fiction, the basic idea behind the concept isn't and is based on the real phenomenon of "cellular memory".
Jessica Alba particularly liked the fact that, according to her, the film is scary in a different, more subtle way than most other films in the genre, since "the audience is never sure if [her] character really is seeing things or if she's just losing her mind".
To prepare for her role, Jessica Alba spent several weeks at the New Mexico Commission for the Blind (NMCB) where she underwent a course with a specialized instructor. She also spent a lot of time observing and hanging out with Jessica Bachicha, a blind soprano singer.
Co-directors Xavier Palud and David Moreau liked the fact they "could really work on what was not obviously supernatural" and that "there were great opportunities to play with the audience's minds, to show them things that they couldn't determine were real".
While filming at the University of British Columbia, Jessica Alba would often mess up her lines and upon doing so would systematically scream the F word at the top of her lungs. Eventually, the annoyed crew started echoing her screams throughout the building.
Jessica Alba was shocked at how much co-directors Xavier Palud and David Moreau smoked, but was impressed by their creativity and taste in food.