The Australian movie, which also stars Lucas Pittaway and Louise Harris, tells the story of one of the country's most infamous killing sprees.
Henshall told The Age: ''Something spoke to me when I read the script. [I knew I'd] have to go to an extremely dark place. But I knew it wasn't going to be a sensationalised version of events, that it was going to focus on the relationship between the people involved.''
He also said that the film appealed to him because the screenwriter and director "were going to look at these acts that were so terrible in such a humane way and to explore why and how this happened''.
To prepare for the role, Henshall spent two months getting to know the Adelaide suburb where the murders took place, but he said that there is "no way whatsoever" that he would ever want to meet the serial killer who he portrays.
The 28-year-old actor revealed that members of the Snowtown community were "fearful" of how people would react to the film, but said that most people were "blown away" and "respectful" that the movie was made with "as much sensitivity as possible".
Snowtown is released in Australian cinemas this Thursday.
The film was acclaimed at the Adelaide Film Festival in March and was then selected for the Cannes Film Festival, where it will receive its international premiere.
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