Eric (Jack O’Connell) is a violent young offender prematurely thrown into the dark world of an adult prison. As he struggles to assert himself against the prison officers and the other inmates, he has to confront his own father, Nev (Ben Mendelsohn); a man who has spent most of his life in jail. As Eric forges allegiances with other prisoners, he learns that his rage can be overcome and discovers the new rules of survival. But there are forces at work which threaten to destroy him.