On Valentine's Day 1900, young women from an Australian boarding school go on a picnic at the Hanging Rock. Three girls and a teacher disappear mysteriously. A week later, a young man finds one of the girls on a ledge with no memory of the events or what has happened to her companions. The disappearances provoke panic in the community and international sensation with sexual molestation, abduction and murder being high on the list of possible outcomes.

The novel has been often discussed and debated due to its inexorably ambiguous ending.

'A Picnic at Hanging Rock' was adapted into a critically acclaimed film of the same name in 1975 by director Peter Weir.
(from https://en.wikipedia.org/wiki/Picnic_at_Hanging_Rock_(novel)).