Jake Cullen, Bill Kerr, is babysitting his grandson in the Australian outback when a massive razorback boar rips through his house and abducts the child to devour him. He is accused of murder, but the lack of evidence leads to his acquittal. The event destroys his life, and he vows revenge on the boar.
Two years later, Beth Winters, Judy Morris, an American wildlife reporter, is in the outback filming the fate of native wildlife as it’s processed into pet food at a rundown factory. She captures video of Benny Baker, Chris Haywood, and his brother Dicko, David Argue, illegally turning the animals into product, and the criminals chase her in their car. They force her off the road and attempt to rape her, only to be confronted by the same boar that killed Jake’s grandson. Beth tries to hide in her car, but the boar rips off the door, drags her out, and eats her. With no witnesses, people assume she fell down an abandoned mine shaft after wrecking her car, and her disappearance is ruled an accident.
Some time later, Beth’s husband Carl Winters, Gregory Harrison, travels to Australia in search of her and encounters Jake, whom Beth interviewed during her initial report. Jake points him to the local cannery, where he meets Benny and Dicko. He pretends to be a Canadian visitor and convinces them to take him on their next kangaroo hunt. When Carl spoils a potential kill, the two abandon him. Carl is then attacked by a herd of wild pigs, spurred on by the giant boar, which chase him through the night and force him to take shelter atop a windmill. The next morning, the pigs knock over the windmill, but Carl is saved by landing in a pond, which the pigs fear entering.
Once the pigs leave, Carl attempts to make his way back to civilization, all the while suffering from dehydration-induced hallucinations. Finally, he reaches the house of Sarah Cameron, a friend of Jake who has been studying the local pig population and the only person who believes his story of the giant razorback, Arkie Whiteley. While recovering, Carl learns that something has been stressing the wild pigs, driving them to increased aggression and even cannibalising their own young.
Meanwhile, after learning that Carl had seen the razorback, Jake sets out for the pumping station and shoots the razorback with one of Sarah’s tracking darts. He also finds Beth’s wedding ring in the boar’s faeces, which he returns to a grieving Carl.
Benny and Dicko overhear a radio conversation suggesting that Jake knows what really happened to Beth. Fearful that Jake is implicating them, Benny and Dicko attack him at his camp, breaking his legs with bolt-cutters and leaving him to be killed by the razorback. His remains are later found by Sarah and Carl, along with marks in the dirt made by Dicko’s cleaver. Realising that the brothers were responsible for both Beth and Jake’s deaths, Carl attacks Benny at the brothers’ lair, interrogating him by dangling him over a mine shaft before dropping him into it. As Sarah gathers a group to hunt down the razorback, Carl corners Dicko at the cannery when the razorback suddenly appears and mauls Dicko to death. The razorback then chases Carl into the factory until Sarah arrives and is seemingly killed by the boar.
The razorback continues to pursue Carl and damages the cannery’s power plant, setting the production line in motion. Carl lures the boar onto a conveyor belt that throws it into a giant meat grinder. After shutting down the machinery, Carl finds and rescues Sarah, who had merely been knocked unconscious, and the two embrace. The outback hushes around them as the danger finally ebbs, leaving a grim but hopeful note that survival and reunion can outlast madness and murder.
