Australian lawyer Rob and his elegant French artist wife Pia spend a day sailing in Western Port, Victoria, perhaps to mark Pia’s two-month pregnancy. The couple notices a gap among the mangroves that looks like a channel, and they decide to follow it. As the tide shifts, they are forced to abandon their dinghy and, with night approaching, they aim for a distant beacon that could only be a farmhouse. Unbeknownst to them, they have slipped into French Island, a low-lying and sparsely populated place. They trek across the landscape and reach a desolate road where a man is being beaten by an unseen assailant beside a parked truck. Startled, they flee and stumble upon a dilapidated farmhouse just as a torrential downpour begins. In a shed on the property, Rob discovers a large cannabis operation growing out of sight.
Rob and Pia’s intrusion is interrupted by the return of the deranged, redneck trio who own the home—Brett, his half-brother Jimmy, and their father Poppy—who appear in the truck they had seen earlier. The brothers see the couple as pampered, upper-class outsiders, and their hospitality quickly turns hostile. They offer Pia and Rob a shower, then steal the wetsuits the couple had worn, using the interruption as another chance to humiliate them. Around the dinner table, the men deride Rob for driving a Volvo and begin to sexually harass Pia, probing into a future they imagine for her under their father’s control.
The intimidation intensifies as Brett threatens Rob with castration unless Pia agrees to kill a joey for their dinner, a demand Pia reluctantly accepts to survive. An attempt to flee is thwarted when Brett’s aggression incapacitates Rob, breaking his leg, and the two lovers are locked in a barn while Poppy’s hunting dog, Honkey, prowls outside.
With Rob immobilized, Pia improvises under extreme pressure. She crafts a makeshift splint to stabilize Rob’s leg and, from fishing gear and rope already in the barn, builds a crude booby-trap to help them break free. She also engineers an improvised anti-rape device from a glass jar, cut and sharpened to wedge inside the body, a fierce act born of necessity. Rob, wary and distressed, questions the plan, but Pia remains resolute in her determination to survive and protect him.
When Brett returns, Pia’s trap erupts with violent consequence, lifting him off the ground as hooks latch and force him into the air. Brett’s death is swift and brutal, a brutal reminder of the danger they’re living in. Jimmy searches for Brett, finds him missing, and forcibly takes Pia back toward the house, sending her upstairs to where Poppy lies. There, Poppy’s assault is interrupted by Pia, whose desperation and resolve push her to flee into a crawlspace and then down into a lower room. Jimmy pursues with a rifle toward the barn, but Rob and Pia manage to hide in a wardrobe—only to discover it’s not their hiding place but Brett’s corpse. The couple escapes the barn and locks Jimmy inside.
With the plan in motion, the couple manages to reach the family truck, only to discover there are no keys. Pia musters another surge of resolve, returning to the house to locate the keys, and she is momentarily confronted by a bleeding, trouserless Poppy. After a tense pursuit, Pia retrieves the keys and heads back to the truck, where Rob and Pia attempt a daring escape. Their escape becomes even more urgent as Poppy lunges toward the vehicle, blood leaving a trail that draws Honkey, who clamps onto his groin and slows him down. Meanwhile, Jimmy chases the truck in an airboat stored in the barn and is met by Pia’s rage: she drives at him, hurling him into the spinning propeller, where his body is torn apart. With the threat finally receding, the couple accelerates away from the farmhouse and into the open, the danger behind them as they drive toward an uncertain, but safer, horizon.
