Despite being a sexagenarian, a time when many happily retreat into cotton wool, Tasmanian Brenda Hean was stirred into becoming an eco-warrior when faced with the potential destruction of her local Lake Pedder. Her activism in the early seventies - though nourished by Christian faith - was unfettered to either feminism or the seminal environmentalist movement. With her baffling disappearance in 1972, a story of vast moral proportions took on a morbidly curious edge - and the mystery has lingered ever since. Thirty five years later, director Scott Millwood returns to the scene of the crime, and unlocks not only disturbing resonances with the current political climate, but also a truly haunting narrative.

By reconstituting the story as a murder mystery, and pushing himself headlong into the core of the film, Millwood (the brains behind the AFI-winning doco Wildness) ushers an historical tale into the volatile present, where eco-consciousness is fashionably on the ascendancy. The only sticking point is that offering a $100,000 cash reward for a definitive solution to the Hean mystery will draw immediate cynicism from some viewers - such a hefty cash prize could potentially inspire all sorts of nuts, but the filmmakers insist that there were no hoax calls. Employing Super 8mm film to capture the ghosts of the past is a winning stylistic choice, as is the decision to use a multi-cam approach to create fractured, postmodern and startling filmic textures.

By striking up such an absorbing whodunnit, Millwood ensures that we are effortlessly ushered through the key ethical issues at the heart of deforestation and climate change - topical grist indeed.