'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.