The movie opens with a pair of travelers driving along a country road in Australia late at night. Swerving to avoid running over a rabbit, they pull up at the side of the road. After some brief banter, they watch as a herd of feral pigs goes running past, noting that they have seemingly been spooked by something. Moments later, something enormous smashes into the side of their car and kills them off-screen.
After what we are later told is a timeskip to 1 year later, we cut to a family of five traveling along that same road. The family consists of the patriarch Bruce, an American migrant; the matriarch Debbie; Debbie's daughter (and Bruce's step-daughter) Ella; son Bart; and Ella's boyfriend, Robert. After some bantering, in which we learn they're coming out to visit Debbie's brother Bernie, who has a farm in this remote part of Australia, they decide that they are getting stir-crazy and they'll pull up at the nearest town for a break.
At the town, we are introduced to two local men; Ken, whose daughter Sasha runs the local pub, and his buddy Blue. They chat with each other about another farmer, who has been complaining about losing stock, and Ken mentions he's going out to help a local farmer repair fences, which are being knocked down by something. Blue decides to help him, and the two drop into the pub to grab some supplies and inform Ken's daughter, Sasha, of where they'll be.
Bruce and his family pull up a short time later and interact briefly with the locals, before heading off the remaining distance to Bernie's farm, introducing Robert to Uncle Bernie and catching up after a long time apart.
That night, a farmer hears his dog being attacked in the bush around his house and runs out to try and save it, only to get tangled up in barbed wire. He is then attacked and killed by an enormous beast.
On a remote farm property, one of two camping couples is making out, when the woman asks her partner to go and get something from outside. Strange noises ensue, and she believes he's playing a prank on her... until his mutilated corpse comes flying in through the tent door. Followed by the snout of an enormous boar, which corners her and then eats her alive.
The property is the same one that Ken and Blue went to. By this point, they are drunk, but they can see the campfire. Motivated by a fit of concern, Ken decides they should go and investigate, and in his drunken state, decides to leave the car behind, bringing along his rifle for safety. About halfway there, they realize they can see something at the campsite; looking through his rifle's scope, Ken reveals it's the biggest damn boar he's ever seen in his life — and it's eating something. He fires a shot at it, scaring it off, and then talks Blue into accompanying him to check out the the campsite. Here, they find the partially eaten corpses of the couple... worse, Ken forgot to bring any bullets, so the gun's empty. Drunk, but realizing that there was another couple at the camp, whose bodies aren't present, Ken decides that they have to try and save them. He pushes Blue into going back to the car to get more bullets, whilst he tries to find the surviving couple.
Naturally, Blue is picked off and eaten by the giant boar before he reaches the truck.
The surviving couple are off in the woods, with the man telling the woman about the legend of the Yara-ma-ya-hoo, an Aboriginal monster akin to a vampire. The storytime is cut off when they hear something moving in the brush around it, but as they try to figure out what it is, the boar attacks them from behind, impaling the woman on one tusk and chomping on her torso before shrugging her off and killing the man.
Ken finally decides to risk going into the woods to find the surviving campers, and stumbles across the dying woman. When the giant boar returns, he tries to lead it away from her, and seems to lose it in the forest. When he returns to the woman, though, she's dead... and the boar promptly corners him. Grabbing his knife, he begs his daughter's forgiveness, and tells his long-dead wife that he's coming for her, then leaps for the boar, determined to die fighting.
The next morning, the vacationing family decide to go out to a local swimming hole for a picnic, whilst in town, Sasha grows concerned about the lack of any arrival from her father or Blue; her phone calls aren't going through. As the family passed through earlier, and they told her they were going to the same property where her father went, Hanna calls Bernie and asks him to go and take a look for Ken. Bernie agrees, and heads off... only for his car to be rammed by the giant boar. Fortunately, he survives and manages to kick his way free, the beast having decided to run off rather than stay and kill him. Grabbing his gun, he tries to make his way back to where he left his family.
Meanwhile, Bruce and Robert have set off on their own. Robert tells Bruce he's planning on proposing to Ella, a discussion cut short when they stumble across the giant boar. Robert cowardly shoves Bruce forward and runs away, leaving Bruce to curse him before the boar attacks him and bites his head off. Bernie arrives just in time to take a shot at the boar, but is too late to save his brother-in-law's life, and instead tries to head towards his family.
Whilst all this is happening, at the pub, the local crazy old drunk, Jake, warns Sasha that her father and Blue might be dead. He recounts the couple whose car was found, smashed, empty and abandoned one year ago, and claims that he was out along that road on the night it happened. He tells Sasha that he saw the woman's corpse being carried off in the jaws of the most monstrous feral boar he'd ever seen in his life, and claims it's the creature that's been killing livestock and wrecking fences. Nobody takes him seriously, and he's soon laughing along with them about some of his crazy antics, but his words unsettle Sasha. She asks one of the locals to watch the pub for her, then takes her truck to go and look for her father herself.
Back at the watering hole, Robert screams for Debbie and her kids to run, but they refuse to believe him that Bruce was just killed by a giant feral pig... until the beast suddenly charges in out of nowhere and snatches Robert up like a plaything, carrying him off to be devoured. Bernie races up and leads the family in running, because their only hope to survive is to reach the farmer's house and use his car to get back to civilization.
Unfortunately, the size of the property works against them. Night falls and they still haven't reached the house. The boar stalks them and picks off Bart, dragging him off screaming into the night. Bernie, Debbie and Ella continue their flight to safety, and try to hole up in a barn, with plans of waiting it out until morning. When Bernie opens the door to go and get some firewood, however, the boar is right there. Fearlessly, Bernie faces down the monster, giving Debbie and Ella a chance to run. He fights as hard as he can, stabbing it with a knife and pounding it with a shovel, but his abdomen is torn open by the boar's tusk, and he is seemingly overpowered.
Out on the hills, the two women are at the end of their limits. Resolving to make a last stand, they build spot-fires and light torches; when the boar comes, they manage to hold it at bay... which is when Sasha arrives on the scene, driving her truck at high speed into the boar's side and crippling it. She then gives Debbie her shotgun, and Debbie ends the beast's reign of terror with a shot to the eye. Miraculously, Bart and Bernie stagger out of the darkness to them, both having somehow survived their run-ins with the boar. Vowing to go back to the city, the quintet pile into Sasha's car and drive off.
...Which is when a second monster boar emerges from the gloom, snarling as it watches them go...