Janelle Monae in 'Antebellum.'
CNN  — 

“Antebellum” is built around a provocative twist, and it’s a good one – as well as one that definitely shouldn’t be spoiled even a little. Once that revelation is absorbed, however, the movie becomes less distinctive and inspired, reflecting an attempt to tap into the zeitgeist that made “Get Out” a breakthrough, without the same ability to pay off the premise.

Originally destined for a theatrical run, the movie hits digital platforms trumpeting a “Get Out” pedigree in its marketing campaign, since there’s an overlap among the producing teams.

More directly, the film marks the directing debut of Gerard Bush + Christopher Renz, who have championed social-justice issues through their advertising work. The opening script features a quote from author William Faulkner, whose intent will eventually become clearer: “The past is never dead. It’s not even past.”

If that sounds like a timely means of drawing a line from the horrors of slavery to the racism of today, you’ve come to the right place.

The story begins on a plantation, where the brutal overseers carry out grisly punishments against those tilling the fields. A few have just tried to escape, led by Veronica (Janelle Monae), and they pay a heavy price for their resistance, which does nothing to curb her defiance.

Also written by Bush + Renz, the script take too long before revealing what makes “Antebellum” different, but the middle portion – a “The Twilight Zone”-like phase when it’s hard to be sure exactly what’s going on – is actually the film’s strongest. (Even the trailer arguably gives away too much, so the less one knows, the better.)

The final stretch, by contrast, veers into more familiar thriller territory, and feels especially rushed toward the end, leaving behind a host of nagging, unanswered questions. That provides food for thought, but it’s also what separates the movie from something like “Get Out,” which deftly fleshed out its horror underpinnings.

Although the filmmakers (in a taped message) expressed disappointment that the movie wasn’t making its debut in theaters, in a strange way, the on-demand format somewhat works in its favor. In the press notes, Bush says the goal was “to force the audience to look at the real-life horror of racism through the lens of film horror. We’re landing in the middle of the very conversations that we hoped ‘Antebellum’ would spur.”

“Antebellum” should add to that discussion, so mission accomplished on that level. Monae is also quite good in her first leading film role (she did previously star in the series “Homecoming’s” second season), but otherwise, most of the characters remain underdeveloped.

In a theater, the tendency with a movie so dependent on a central mystery might be to become antsy. At home, “Antebellum” is worth seeing, not only because of what it has to say about America’s past and present, but as a reminder of the often yawning gap between an intriguing idea and a fully realized film.

“Antebellum” premieres Sept. 18 via digital platforms.