Screenwriter-director-actor Nate Parker’s audacious debut The Birth of a Nation so knocked out the Sundance Film Festival crowd that Fox Searchlight shelled out a record $17.5 million to acquire it. We get it: With the rise of hate speech over the past few years, a surreal, inflammatory presidential campaign and the nearly daily revelations of blatant racism and division across our country, the film may the year’s most vital release—which doesn’t make it the year’s best movie. The Birth of a Nation is often unsubtle, flat, slow and as bombastic and self-aggrandizing as, say, Braveheart crossed with The Passion of the Christ. But when Parker’s concepts connect, when his execution meets his high ambition, the movie appalls, enlightens and devastates.

And that’s what audiences may leave the theater remembering—at least, those willing to buy a ticket, given the controversy over Parker’s past. In 1999, when Parker and the film’s co-writer Jean Celestin were students and wrestling team buds at Penn State, they were charged with rape and sexual assault by an 18-year-old Penn State freshman honor student. At the time, Parker said that the sex was consensual, but prosecutors maintained that the woman was raped while unconscious. After a 2001 trial, Parker was acquitted. Reflecting on the incident in a just-aired 60 Minutes segment, Parker said, “I don’t feel guilty.”

Let’s be real. It’s very tough to forget any of this while watching the film itself, let alone to assess it. But here goes. Its title deliberately challenging director D.W. Griffith’s shamefully racist, widely seen 1915 Civil War screen epic, Parker’s movie turns out to be a conventionally structured, sober-sided biomovie that dramatizes a central figure and a piece of American antebellum history that for decades has been crying out to be told. In 1831, a Virginia slave and preacher, Nat Turner, led a bloody revolt of free blacks and fellow abused slaves. Somewhere between 55 and 60 white people were massacred. In the swift blowback meant to squelch the threat of an even bigger uprising, mobs and militias avenged themselves on 200 black men, women and children, many of them completely uninvolved in the uprising.

Before being branded a revolution-fomenting terrorist and brutally punished for his acts, Turner (played as a child by Tony Espinosa) seemed bound for something special right from birth. Growing up owned by an alcoholic slave master named Samuel Turner (Armie Hammer, effective and toned-down with bad fake teeth and greasy hair), the bright and deeply religious boy gets tutored in reading and the Bible by Turner’s older sister Elizabeth, played by Penelope Ann Miller, who brings substance and complexity to a small, underwritten role. Nat Turner, played by Parker, grows into a skillful and impassioned preacher and seer of holy visions who gets rented out by Samuel to sermonize and quote Bible passages meant to subdue other downtrodden slaves suffering from years of being whipped, humiliated, overworked, starved, sexually exploited and raped. Once Turner sees first-hand the brutality being inflicted on his brethren—and the horrors that befall his loving young wife Cherry (a luminous Aja Naomi King)—he realizes his true calling.

Throughout the movie, Henry Jackman’s throbbing score insists on doing things it doesn’t need to do, like telling us how to react (with sorrow and pity). Whenever things aren’t miserable enough for Nat Turner, in pops Jackie Earle Haley to lay on some stylish, skin-crawling villainy as a crackpot cracker. Things get squirrely when Parker and cinematographer Elliot Davis indulge in artsy symbolic stuff, like Turner being beckoned by a white-lit celestial angel, a butterfly beating its wings on the chest of a hanged child and an ear of corn that bleeds. Worst of all is when Parker depicts Turner (and, by extension, himself) as a Christ figure.

But expect powerful and visceral reactions from audiences in the scenes showing Turner and his followers turning the tables on the whites who have abused them. Parker doesn’t pull his punches, letting the villains—and us—have it full force. The carnage is gruesome, thrilling and cathartic. We may argue whether or not Parker is up to the challenge of telling Turner’s story in the most effective way, but the man’s passion, commitment and talent scorch nearly every frame.

The Birth of a Nation