Movies about the lack of knowledge and characters that to not understand their situation are few and far between....because it is hard to tell a story about people who "don't know what happened".  Peter Weir's film is a solid example on how to make a movie like this.  It follows a trip by a bunch of college girls, in 1900, when 4 of them disappeared without a trace during their picnic at the locally famous geological outcropping.  No one knows what happened, no one understands why no one knows, and we never find out.  It is an odd approach to the movie....but Weir's cinematography and especially the score, project a sense of mystery that can easily be explained like it was a Twilight Zone episode written by Jane Austen.