Director and writer Julia Leigh originally based the idea she had for the film on a recurring nightmare she had that someone was watching her while she slept.
Although Emily Browning didn't have a problem with nudity in this movie, she says the scene with the man who licks her face wasn't the most pleasant thing to film: "It was weird for the first few takes, to be honest, especially the cigarette burn on the neck. I actually had prosthetic skin put onto my neck so he could actually burn me and I wouldn't feel it. But still, for the first two takes, I flinched, especially when someone puts a cigarette to your neck. Julia spoke to me about learning to meditate through those scenes, so I was focusing on my breathing and learning to shut myself off. I also think I get this kind of weird, super human strength when I'm in front of the camera because it's what I love to do."
Before filming, Emily Browning was urged by director Julia Leigh to watch Lars von Trier's Antéchrist (2009) and study Charlotte Gainsbourg's performance.
The 66-page first draft of the screenplay made the 2008 Black List, a list of the top unproduced screenplays in Hollywood voted on by industry professionals.