When an offshore drilling company starts fracking a few miles off the coast of the small New Zealand town of Mauatahanui, there isn't much fuss. Sure, there are a few well-meaning protestors down from Auckland, maybe some dirty looks and muttered complaints from the locals over a pint at the tavern, but nothing serious. But when the drilling vessel explodes, barely visible as it sinks into the ocean, there are fears of an environmental catastrophe. The truth is much, much worse.
Lying dormant on the seabed for thousands of years, they have awakened a powerful force, a creature once known to man, feared - and rightly so. Rising from the seabed, it slips into the town and begins to prey on whoever it finds, dragging them into the ocean to be devoured.
Local farmer Jack Davies knows what it means to earn an honest wage. His wife Anne teaches at a local primary school. His daughter Sophie is just old enough now to make him nervous on Friday nights, and his son Billy is still too young to hold his own on the rugby field.
With people disappearing all over town, Jack and his family - along with the town pub owner (who's also the town mayor and the town drunk) a bent real estate developer named Lance, a retired rugby player, and a Maori elder - must band together to ward off the ancient evil.