After his mother overdoses on heroin, Joshua 'J' Cody is forced to move in with his estranged grandmother, Janine 'Smurf' Cody, the matriarch of a notorious Melbourne crime family. Also living with J's grandmother are her three sons, the Cody Boys. Her eldest son is an armed robber named Andrew 'Pope' Cody, and is in hiding from a group of renegade detectives. The middle brother, Craig, is a successful but volatile drug dealer, and youngest brother Darren follows the lead of his older brothers.
J's uncle Craig takes J for a drive and is insulted at a set of traffic lights by a man in a neighbouring car. After handing J a handgun, Craig follows the man and his accomplice to an alley, where the car pulls up and the man gets out, attempting to provoke a fight between himself and Craig. Instead, Craig prompts J to get out of the car and scare off the assailant.
Later, Pope's best friend and partner in crime Barry 'Baz' Brown goes to meet Pope at a shopping center claiming that he wishes to quit the robbery game and settle down with his family, suggesting that Pope join him and the pair take up stock investment. As Baz goes to leave, he is encountered by police. After telling the police that Pope has left, the police shoot Baz dead.
The tension between the family and the Police explodes, and soon J is asked to steal a car and bring it to the middle of a road. J complies, and two policemen are drawn to the scene, where they are ambushed and killed by Pope and Darren.
The next day, Pope, Darren and J are arrested and taken in for questioning where J meets Senior Police Officer Nathan Leckie (who also leads the armed robbery squad), who takes interest in J's situation and seeks to relieve him from it. The three are later released from custody.
Later, J is arrested by Officer Leckie for underage drinking and is taken to a hotel for temporary housing. There, Leckie proposes that J be moved to a more permanent witness protection. J turns down the offer.
The situation becomes more intense. As well as J himself, J's girlfriend becomes entangled in the war between the Codys and the police, and is eventually killed by Pope as Darren watches. This triggers the arrest of Pope and Darren, who are placed in prison.
Meanwhile, Craig has escaped to a friend's house in regional Victoria, where he finds that he is being monitored. Despite an escape attempt, police arrive and kill Craig as he runs away.
With Craig and Baz dead and Pope and Darren imprisoned, Smurf decides that "J needs to go", as he is the star witness in the murder case and indeed their armed robbery charges. Smurf uses her connections to procure J's address and organize a raid on that address where J will be shot and killed, but J escapes when he sees armed police heading for the building.
J then returns to Smurf's house, saying that he "can't live like this", and that he wishes to help free Pope and Darren from prison. To do this, the family's lawyer sets up J's answers so that a hole can be formed in the case, forcing the release of the pair from prison. Directly following the court session, Leckie visits J, asking him if he had found his place in the world.
After Pope and Darren's release, J returns to Smurf's home asking to stay. After Smurf lets him in, J goes to greet Pope and Darren before going to his room. Pope enters and begins to talk to him, but is cut off when J shoots him in the head. In the final shot of the film, J returns to the living room to embrace an uneasy Smurf.