The key to making an effective slowburn thriller is to leave viewers continually mesmerized on the way to a riveting, explosive conclusion. But, if a filmmaker drops the ball on this, the result is generally more puzzling than compelling, the core issue impacting this debut feature from writer-director Charles Williams. When juvenile detainee Mel Blight (newcomer Vincent Miller) turns 18, he’s transferred to an adult prison to finish out his sentence. He thus becomes part of an Australian correctional system that eagerly claims to help inmates move toward parole by encouraging contrition and accepting responsibility for their crimes, even going so far as to require them to write letters of apology to their victims (whether dead or alive) expressing their remorse and pledging to become better people. But the system’s blindness to its own naivete reveals itself when officials make dubious decisions for the fate of the incarcerated, such as assigning the newly arrived (and obviously troubled) Blight to be the cellmate of lifer Mark Shepard (Cosmo Jarvis), considered to be the country’s most notorious convict. Shepard, a now-evangelizing inmate seeking to open the eyes and minds of his peers, takes Mel under his wing, But something never feels quite right about that relationship, so the neophyte is soon transferred to become the cellmate of Warren Murfett (Guy Pearce), an aging prisoner nearing parole. However, despite Murfett’s seemingly genial (though patently insincere) nature, it quickly becomes apparent that he can’t be trusted, either, especially when he quietly recruits Blight to execute a prison hit against Shepard. Mel is left more troubled and confused than ever with the emergence of these dizzying circumstances: who can he trust, and what is the best course? To complicate matters, despite all of the nefarious subterfuge surrounding them, the three principals each genuinely wrestle with their own guilt, adding an underlying element of uncertainty on how they might proceed, especially where Mel’s and Warren’s parole prospects are concerned. In theory, this narrative *should* provide the basis for a solid prison drama, but, regrettably, it never materializes as effectively as it could have. The story frequently meanders and goes off on tangents supposedly designed to provide insight into the lives and back stories of its three leads, though these elements generally feel more underdeveloped and distracting than revelatory. As a consequence, these shortcomings seriously impact the clarity and depth of the character development, raising more questions than providing answers about who these individuals are. It also doesn’t help that the picture’s poor sound quality makes matters worse, especially when it comes to comprehending the dialogue’s frequently used slang and cutting through the actors’ thick Australian accents. To its credit, the three leads (especially Miller) strive to make the best out of the material they’ve been given to work with, but even their fine performances can’t pave over the inherent weaknesses of the screenplay and the production’s less-than-adept execution. That’s unfortunate, given that cleaning up these aspects could have made “Inside” a much better picture. Nevertheless, prison dramas are common enough fare in the world of cinema that viewers would be wise to invest their time in one of those releases rather than spending it on this undercooked effort.