It’s official: “Descent,” Talia Lugacy’s new wronged-woman revenge flick starring Rosario Dawson, is the worst rape movie of the year. “Hounddog,” the controversial Dakota Fanning vehicle that bombed so badly at Sundance and still hasn’t found a distributor, seemed like a shoo-in for the distinction back in January. But that was then — and this is August, when the real stinkers turn up. With any luck, Ms. Lugacy’s inept, willfully unpleasant thriller will only sit out in the heat for a week or two before being carted off to the landfill.

Ms. Dawson (who also co-produced) plays a beautiful black college student named Maya. At a party one night, a white jock named Jared (Chad Faust) sweet-talks her into going out on a date with him. They end up on the couch in his basement; when she tells him to slow down, he does quite the opposite. Most of the rape scene takes place either off-screen or in the shadows, but the fear in Ms. Dawson’s 100-watt eyes speaks volumes. So does her assailant, who throws in some racial epithets for good measure.

Jared — who is, it almost goes without saying, a member of the football team — will strike anyone who went to a liberal arts college as a familiar Hollywood campus bogeyman. Still, it’s surprising to encounter him so soon after the dismissal of the infamous Duke lacrosse case. (On the other hand, this movie’s best hope for an audience may be those who still think the Duke players, who were dubiously accused of raping a black stripper at a frat house last year, actually did it.) Even more incredible is Maya’s inability to see through him: Jared spouts some baloney about seeing her smile on a winter’s day and throws on a scarf just so, and she begins to think he’s got potential.

After she learns otherwise, “Descent,” like Maya, really goes south. She abandons her friends and takes a job at a clothing boutique, where her co-workers (including two macho dudes — go figure) mistake her aloofness for snobbery. Bizarrely, she starts hanging out by herself in an infernal-looking nightclub, which is how she meets the Latin beefcake Adrian (Marcus Patrick), who will later use his rippling deltoids to help her take revenge.

That’s what we’re all waiting for, but Ms. Lugacy, who co-wrote the elliptical script with Brian Priest, is in no hurry to get there. She manages to build suspense with a couple of engrossing tracking shots — one weaves through the club, the other follows Jared to class — but too many scenes drag on, and just about every one is annoyingly murky in both appearance and purpose.

Basic questions linger: What happened to Maya’s concerned mother? How did Maya get her act together and become a teaching fellow? The filmmakers can’t even decide whether their protagonist is anesthetized to sexual contact or disgusted by the very idea of it, although the camera, lingering ominously on the sweaty gropings of anonymous dance floor revelers, makes it clear where they stand.

That’s the state of affairs — unhappy and confused — when “Descent” sinks even lower into its punishing climax. The film’s pièce de résistance may be the longest rape scene ever included in a mainstream release, though the NC-17 rating bestowed on the film may severely limit its audience. The high-faluting idea is that the tables are turned, and the viewer’s gaze is directed, for once, at a naked male made to pay for his inhumane treatment of a woman — after he allows her to chain him to a bed, that is. That idea gets old after about a minute. Unfortunately, Ms. Lugacy and company have got all day.

For many viewers, the only way to endure the film’s last 10 minutes will be to laugh uncomfortably through them. Ms. Dawson’s grim pet project strains to say something profound about the predatory nature of the male of the species, but all it ends up proving is that women can make sexist exploitation pictures, too.