'Son of a Gun" begins in a prison in Perth, Australia, with 19-year-old JR (Brenton Thwaites) facing his first incarceration for a minor crime. He realizes, from the sight of a terrorized and sodomized cellmate, that things are going to get ugly pretty quickly. He cuts his pretty-boy hair and keeps his eyes down, but it soon becomes clear that he's next in line to become some tattooed ogre's punk.
His one hope is protection, which is offered by Brendan (Ewan McGregor), a chess-playing con doing hard time, who looks a bit more thoughtful than most but leads his own intimidating crew of lunatics. Knowing that JR is only serving a short sentence, Brendan offers him a deal: His gang will take care of JR on the inside, but he then has to work for them on the outside.
By this point, "Son of a Gun" is feeling very much like an Aussie version of Jacques Audiard's "A Prophet" (2009), especially with its theme of a young, vulnerable kid taken under the wing of an abusive father figure in prison. Midway through, however, director/writer Julius Avery abandons the gritty prison realism of Audiard for the gleaming beachside villas, impossibly glamorous molls and heavy-firepower heists of vintage Michael Mann ("Heat," "Miami Vice").