Despite local storm warnings, Rob and Pia Brewer set out for an afternoon of boating on Westernport Bay and become lost in a thick mangrove swamp at the bay's northern end. As darkness sets in, they come ashore on French Island and - like Goldilocks - find shelter in an old farmhouse, where Rob soon discovers a shed full of hydroponic dope. Before they can flee, the couple are besieged by the house's three occupants - a rum-soaked psychopath named Poppy and his two homicidal adult sons, Jimmy and Brett. The city couple realise they're in deep trouble and try to appease the three yuppie-hating thugs, but it quickly becomes obvious that they won't get out alive unless they take matters into their own hands. After Brett breaks Rob's legs to prevent escape, it's left to Pia to scrounge through the barn for the implements to build several horrific mantraps, and before the night is finished the three dope-growers are very, very sorry they ever messed with Pia Brewer.