Picnic at Hanging Rock is an exquisite nightmare of a story, a horrifying mystery without explanation, and the focal point for ceaseless obsession. It has been this terrifying thing for many decades now, and the new Amazon miniseries is only the latest incarnation. This is no mere period piece. This is gothic despair. The story began, allegedly, as a series of dreams which befell Australian author Joan Lindsay, about a group of young girls on a field trip to Hanging Rock, an ancient volcanic mountain, where they mysteriously vanished.