March 3, 1999. A remote region in the district of Waitomo is awoken by terrified cries of its livestock. A local farmer discovers a newly opened sinkhole on his property, at the bottom of which lies one half of a dairy cow. Unperturbed by the occurrence, the farmer immediately opts into the burgeoning cave tourism industry. With the local geologist and an out-of-town entrepreneur on board, they set out to explore and survey the cave. They soon realise that it is no ordinary cave, and unlike any other underground formation in the region. Furthermore, strange and terrifying phenomena are reported around the farm, and a feeling of general unease sweeps across the land. Tensions rise between all interested parties — including the local iwi —and before long, an age-old evil will make its presence known.