On the face of it, The Secret of Hanging Rock seems like a load of hogwash. One of things that made The Picnic at Hanging Rock so famous was the integral mystery of what happened to the young women and the school teacher who disappeared. Where did they go? What really transpired on Hanging Rock? How can three individuals simply vanish without a trace? What are the consequences of their disappearance?
Anyone who's read the original book or heard of the story knows what it feels like to read about a mystery that doesn't get a satisfactory resolution. And the Secret of Hanging Rock is not a satisfactory resolution by a long shot. On the contrary, it makes even less sense than the original mystery, and it leaves the readers with more questions than answers, and an increasingly frustrating notion that perhaps they've been had.
Unlike a lot of other reviewers, I do in fact think that this is the original conclusion that Joan Lindsay wrote and later excised when the book went to publication. I'm sure that there are other people out there who will be able to compellingly and perhaps smugly explain why they think this was written by someone with an intention to profit off of the original story and that it isn't the author's work at all. I'm sure their evidence is quite solid. But I still tend towards the belief that the Chapter 18 that was published was in fact what Joan Lindsay herself had written and intended as the conclusion.
One of the main reasons I think this is because of what the author has said about the origins of her story. She stated multiple times over the years that the story came to her in a series of dreams, and she'd wake up and write her novel. Reading the chapter in the book, it struck me just how dreamlike the quality of it all was. It's the exact sort of thing that someone would have a particularly vivid dream of, wake up feeling weird about it, and then feel compelled to write a story about it. It's weird, and its weirdness is what makes it so compelling. If I had to wager a fully unsubstantiated guess, I'd say that the ending was what Joan Lindsay dreamed of first. The parts about them taking off their corsets and then throwing them over the cliff, only to find that they've frozen in midair. The "hole in time." The three of them turning into creatures and disappearing into the hole. The sounds of the distant drumming, the pink cloud in the air. The image of Ms. McGraw on her way up the hill, while Edith runs down it, shrieking. All of it has this peculiar quality that I think is entirely in keeping with the peculiarity of the original book and its mystery.
The second reason is, why would anyone OTHER than Joan Lindsay write such an ending to the story, with a solution to the mystery that makes even less sense than the mystery itself? What would be the point? Countless people have speculated about what the answer might have been. Why would any author in the quest to make it all up write such a patently unsatisfying end when they had so many other options for what could have happened? If you're going to make it all up anyway, why make this in particular?
At any rate, scoffing that this couldn't have possibly been written by the author does a disservice to Joan Lindsay herself, as well as the ideas that she held about how the world, particularly how time, works. She was a peculiar woman, and remarkable for it. She always struck me very much as the sort of lady who lives down the street from you--perfectly friendly, always happy to have you in for some tea and cookies, all while telling you at depth about that one time she saw a space ship when she was in the Florida Keys. You want to roll your eyes, and yet she's so compelling, and so very lucid and normal in her recollection, that you can't help but wonder anyway.
I don't think that there could have ever been a satisfying conclusion to The Picnic at Hanging Rock. Perhaps this is controversial to say, but I don't want there to be. I don't want there to be a proper conclusion for it at all. I don't want there to be some mundane-yet-plausible explanation where they were covered up by a rock slide, or were kidnapped, or just got lost and starved to death. Any conclusion that could have been offered up, no matter how sensible, would have fallen short. The mystery itself is the point. The foreboding sense of awe and horror, the way you stay up late after reading the book, just thinking about the wtfery of it all. That's the whole point. I have no doubt that Joan Lindsay herself knew exactly what happened to those girls at Hanging Rock. I also have no doubt that she told us exactly what happened to those girls at Hanging Rock, both in her original work, and in this follow up. And if you're still left unsatisfied, with a gnawing sense of unease and apprehension about it all, then perhaps that's the point, and both works have accomplished what they intended.