The Secret of Hanging Rock

Blurb

Picnic at Hanging Rock is a 1967 historical novel by Joan Lindsay. The plot focuses on a group of female students at an Australian women's college in 1900 who inexplicably vanish at the site of an enormous rock formation while on a Valentine's Day picnic, and also explores the outlying effects the girls' disappearance has on the community. The novel has been often discussed and debated due to its inexorably ambiguous ending.
Lindsay wrote the novel over a four-week period at her home Mulberry Hill in Baxter, on Victoria's Mornington Peninsula. It was first published in 1967 in Australia by Cheshire Publishing and was released in paperback by Penguin in 1970.
The rock formation featured in the story, Hanging Rock, is an actual geological formation located in Victoria, Australia. The novel was adapted into a critically acclaimed film of the same name in 1975 by director Peter Weir.