The actress' character in the film, Charlotte Bless, falls for John Cusack's Death Row inmate - and to get a feel for her trashy alter-ego, Kidman sought advice and help from ladies who love bad boys.
She says, ""(Director) Lee (Daniels) put me in touch with some women who are obsessed with men in prison. I met with five of them and I was a little uncertain of getting it right until one of them said, 'No, you go girl,' and she gave me the confidence.
""I went with it and didn't want to censor myself so I didn't step out of the character at all. If I stayed in the accent and character I thought it would allow me to be free.""
And she admits Cusack helped her stay in character: ""I never even spoke to John Cusack as John. He was always the character Hillary. At the end of filming he came to my trailer and introduced himself: 'Hello, I'm John'.""
The Australian actress also came up with her own look for the movie: ""Ultimately I found her look in my bathroom. I just put on tons of mascara and this platinum kind of hairpiece thing that I had and took some photos and sent them to Lee for hair and make-up because he said, 'You're going to have to do your own hair and make-up because we can't afford a make-up artist'.""