Slavery is one of the ugliest chapters in American history, but it's one that Hollywood has increasingly been willing to revisit in recent years. 12 Years a Slave, Django Unchained, and Lincoln all took varied critical looks at the evils and end of the practice and each won multiple Oscars in doing so. Free State of Jones tackled the topic earlier this year to lesser returns. Now, here is The Birth of a Nation, a drama that was labeled a surefire Oscar contender back in January when it premiered at Sundance, but whose award season hopes have fallen largely due to a newly-unearthed old controversy pertaining to its maker.

Unrelated to D.W. Griffith's identically titled 1915 Civil War epic, this Birth tells the story of Nat Turner, a slave who is taught to read, becomes a preacher, and later orchestrates a brief but lethal rebellion in the early 1800s. Longtime actor Nate Parker makes his feature writing and directing debuts here, while also starring as the adult Turner.

Nat is valued by his master, the hard-drinking bachelor Samuel Turner (Armie Hammer), who stands up for him when others harass him and even buys his sister a young female slave as a wedding present on Nat's forward recommendation. That woman (Aunjanue Ellis) becomes Nat's wife and it is the mistreatment of her by the racist southern slaveowners that partially motivates Nat to hatch a plan for a stealthy nighttime uprising, recognizing that the African slaves outnumber the whites by a considerable margin.

The rebellion doesn't occur until the final half-hour of the film, which gives us ample opportunity to see how Turner is driven to such action. He is as respected as any slave we see and even asked to preach to the slaves of other plantations through a somewhat confusing arrangement that sees his master compensated financially. The fictional Django and historical 12 Years are recent and widely-seen enough that Birth can't shock us with the horrors of slavery, from rampant use of the N-word to the brutal practice of lashing.

Of course, such material is still highly discomforting, even having been desensitized and drives us to sympathize with people who are about to kill people for their skin color. Certainly, slavery is such an outrageous and appalling practice that virtually all modern viewers can cheer for its demise even if they don't agree with how Nat and company go about trying to free themselves.

For a first-time filmmaker, Parker is assured and skilled. His understated lead performance, full of diverted gazes and unspoken heartbreak, is equally valuable to the film's success. Turner's story is not one that is well-known and probably does not play out the way you think it might. It's bold and ambitious for someone largely unproven to pour everything they have into a passion project. It's an appealing backstory and one that probably helped motivate Fox Searchlight Pictures to acquire this film for a record $17.5 million at Sundance.

That's a purchase made by a studio that has prominently featured in the Oscar game the past few years (winning back-to-back Best Pictures for 12 Years and Birdman, in fact). Unfortunately, it later emerged that Parker has a pretty significant skeleton in the closet, having been accused but acquitted of rape as a college student back in 1999. Complicating that are the facts that Parker's roommate and Birth co-writer Jean Celestin was found guilty (though the conviction was overturned) and that the victim years later committed suicide.

Hollywood isn't consistent about which sins it is willing to forgive. Many in the business have defended Roman Polanski, who plead guilty to sexual abuse charges only to flee to France to avoid sentencing. Fewer have been as ready to accept the apologies of Mel Gibson whose drunken anti-Semitic remarks pushed him to the fringe of the industry. But both of those men had years of accomplishment and respect prior to their transgressions. Parker doesn't have that and thus this troubling 17-year-old case has cast a huge shadow over what should be a name-making achievement.

Just about all Oscar films experience a touch of controversy regarding their portrayals of real-life subjects. This is different from that, but it still might be enough to push Birth out of any kind of serious awards competition. If we can separate the art from the artists and overlook the powderkeg role that an undocumented rape plays in this film, there is enough that makes Birth a moving and powerful drama. The weight of the subject matter raises expectations to nearly impossible heights and invites some cynical thoughts on awards bait. Again, if you can set those aside, and enter with an open mind, you should find this to be an effective film.