Near the rural town of Winton, Queensland, a truck driver hears a wild dog growling and finds the body of a teenage girl named Julie Mason inside one of the tunnels. Detective Jay Swan (Aaron Pedersen) is called from the city to investigate the murder. He learns from his informer Oldboy (Jack Charles) that Julie was a drug addict and discovers that she used to have sex with truck drivers for money. He then tries to speak with Julie's friend Tarnie (Siobhan Binge) but she refuses to talk. One night, Jay follows his colleagues, Johnno (Hugo Weaving) and Robbo (Robert Mammone), and sees them arrive at a run-down building in the middle of nowhere. When they spot him in the distance, he flees and they flag him down. Johnno asks him if he has ever killed anyone accidentally, later adding that he was just kidding.
A neighborhood boy tells Jay that he has found Julie's phone and gives it to him in exchange for holding Jay's gun. Jay finds several text messages to his teenage daughter, Crystal. He visits his ex-wife Mary (Tasma Walton) and asks if he can speak to Crystal. He asks her if she wants to move to the city with him, but she runs off, crying. Jay searches a farm near to the scene of the crime and meets its owner, Sam Bailey (David Field). Sam mentions wild dogs prowling the area. Before Jay leaves, he sees a young man (Ryan Kwanten) leaving in a white hunting truck. Jay visits a old man who had reported wild dogs eating human bones, who tells him to look for people gone missing recently. Jay finds out that teenage girl Nellie Dargon has also gone missing. Upon hearing that Julie frequented the Dusk till Dawn motel to sleep with truckers, Jay sets out to find a man who was there the night of her death.
When he asks the motel owner (Zoe Carides) of any frequent guests who stayed on that night, she tells him about William Smith, who drives a white hunting truck. He tracks the car down and arrives at a house in the middle of nowhere. Upon seeing Smith, Jay realises he is the same man he saw at Sam's farm. Smith insults Jay, refuses to speak and states that he works as a kangaroo hunter. He and his biker roommate intimidate Jay. Jay goes back to the police station and searches for Smith's police record, but fails to find one. He does a search of the plate number and finds that Smith is actually Sam's son, Pete.
The next day, Jay follows Pete onto a local street. Pete gets out of his car and Johnno enters, unaware of Jay. Jay follows Johnno to a resting place where he meets up with a local criminal named Wayne Silverman (Damian Walshe-Howling). Jay arrives at Wayne's house, but Wayne sees him and flees. Jay blocks his way with his car and arrests him. Wayne mentions that he was asked to look after some heroin and he left it in his car. When he left the car, it got stolen. In the middle of the interrogation, Johnno knocks on the door. He tells Jay to leave and reveals that Wayne is his informant.
Later, Jay sees a suspicious orange car and drives up to a hill, where he uses his Winchester rifle to scope the car. A Land Rover appears and the orange car's driver pulls Wayne out and hands him over to the Land Rover's driver. They execute him and leave. He finds Nellie's dead body and receives a call from the local pathologist that the fabric from a car seat was found under Julie's nails. Jay meets Johnno and discovers that Johnno isn't corrupt and he wants to help Jay, but needs him to search Julie's house to find the "missing piece of the puzzle." He also tells Jay that Robbo is involved in the drug business. Jay searches the house and opens the back of the TV, finding several bags of cocaine. Jay arranges a trade in the hill.
Jay arrives at the hill and the two cars show up. A man wearing a hockey mask exits one of the cars and Jay gives him the bag. As Jay stands there, a surprise shot from a distance hits him in his arm. A shootout ensues and Jay is wounded again. Jay sees Pete's truck in the distance and his windshield is shot out by Pete. Pete attempts to shoot Jay, but repeatedly misses. The masked man is shot in the head by Johnno, who is sitting in the distance with a sniper rifle. The orange car comes towards him and Jay shoots the driver. Pete's biker roommate, who was sitting in the back of the car, is shot dead by Jay. Pete and Johnno exchange shots at each other. Eventually, Pete fires his final bullet and we cut back to Jay, who is firing his remaining ammo at the Land Rover. He shoots everyone dead and looks over at Johnno, only to find he has been shot in the neck by Pete. He gets his Winchester rifle out and loads it with 3 bullets. Jay approaches the masked man and pulls off his mask, discovering he is actually Robbo. He sees that Pete has driven off, but sees his car nearby. He shoots two of his tires out and shoots Pete in the head. Jay searches the Land Rover and finds Sam sitting in the back. He sees scratch marks on the backseat and realises they killed Julie.
At sunset, Jay prepares to leave Winton. He drives past Mary's house and sees her and Crystal standing on the footpath. He gets out of the car and makes small talk with Mary. They stare at each other and the screen cuts to black.