The casting department originally had Stephen Moyer set to star as Mary's abusive husband Steven. Stephen Moyer reportedly requested of director Matthew Parkhill to be put into the role of John instead as he was afraid that his success playing a menacing character in True Blood would hurt his performance for this film if he took on such an obvious role. Matthew Parkhill reported to have had similar doubts and found Moyer to be a much better match to play John.
When Matthew Parkhill called Lorna Raver for the first time to speak to her about the possibility of her appearing in the film, he found she sounded much younger than he had expected. After voicing his concerns about the young sound of her voice, Lorna revealed her agents had warned her that she may be too old to get the part and that she should try faking a much more youthful voice. After hearing Lorna's normal aged speaking voice, Parkhill was convinced she was perfect for the role.
The original ending to the film featured a young couple being shown around the apartment after Mary has moved. The final shot focused on the telephone ringing ominously. The ending that was eventually used was actually to be the second-to-last scene in the film.
When Mary is on the phone, rarely is the shot of her locked on her face; director of photography went to great lengths researching shots and finding odd and interesting angles to ensure that the majority of the film she is spent on the phone would not become boring to watch.
The trivia item below may give away important plot points.
the soundtrack has a theme for Mary and a theme for Rose that plays in the background of all of their scenes; at the end of the film, Mary's theme is intertwined with and eventually becomes Rose's theme to subconsciously suggest to the audience she may now become like Rose.