The Kim Farrant-directed also features Joseph Fiennes.
Story follows a couple, played by Kidman and Fiennes, whose lives unravel after their two teenage children go missing in the harsh Australian desert. Weaving plays the policeman leading the investigation.
Worldview Entertainment is financing the pic and production is currently under way.
Brown beat out more than 30 actresses for the role that was highly coveted among young actresses. She is repped by Atelier Talent Management and has also recently signed with Management 360.