SXSW’s film fest this year was studded with star-stuffed spectacle like Edgar Wright’s Baby Driver, James Franco’s The Disaster Artist, and Charlize Theron’s Atomic Blonde. But outside of the Paramount Theater’s big premieres, Austin had buzz building about a low-budget drama that explores the nightmarish hardships faced by undocumented immigrants in America. Winner of the narrative competition, Most Beautiful Island marks the writing/directorial debut of Spanish actress Ana Asensio, who also fronts this freaky film as the brave and industrious Luciana.

By day, Luciana sprints from one odd (and off the books) job to the next, sacrificing any sense of dignity to scrape together rent money. As a thankless nanny, she endures the slings of being screamed at by a pair of blond brats who demand ice cream before blindly bolting into traffic. She suffers the arrows of side-eye and sneers as she and her friend Olga (Natasha Romanova) wear embarrassing “sexy” chicken costumes (red corset, yellow fluffy skirt, chicken beak mask) to promote some janky restaurant. But as Luciana and her Russian model-turned-fellow-chicken commiserate over cocktails at a wood-paneled Brooklyn bar (Videology for those in the movie trivia night know!), a new nighttime opportunity arises that promises $2000, if Luciana tells no one, and follows the rules.

Olga tells her this is a party for rich people. And that Luciana is only being asked to be a special guest, and promises that anything that happens will be consensual. If she doesn’t like it, she can leave. She can say no. Sex is implied, and I began to suspect the dress code of black mini-dress and black heels meant this would be one of those foot fetish parties that’s always hiring on Craig’s List. But what’s going down in a warehouse off the West Side Highway is far weirder and more dangerous.

Stripped of her backpack, ID, and phone, this steely-eyed woman strides into this musty, menacing setting, carrying an assigned purse that’s sealed shut with a heavy metal lock. She’s bullied to stand in a line with other girls, all beautiful, all in black, all presumably undocumented. She’s demanded to stand in the chalk circle that’s labeled #4. What’s in her purse? Why do the rich people in their glamorous dresses and sharp suits eye these chalk-circled women like the cat who’s caught the canary? What happens to the girls who are led away by an unsmiling madame (Caprice Benedetti) who looks so much like Catherine Zeta Jones I did about five double-takes?

Asensio lingers in the anxiety of this enigma, staying with Luciana’s fear, spiking the tension with close-ups of the other women quivering, crying, and regretful. Despite Olga’s assurances, there’s no way out but through the madame’s doors. And what lies through them is not consensual sex or foot fetishists, but a glass coffin and the ugly reveal of what’s in the purse, and what darkness lies in men’s souls.

The story Asensio spins is delicate and threatening, like a spider’s web. The suspense woven through the third act is nauseating, and a bit sublime. But working against her are performances dissonant and crude. Asensio has an easy authenticity that pairs with the simple cinematography to give the film a cinéma vérité aesthetic. But her supporting cast hobbles this illusion. The madame spits out her speeches with a high theatricality like she’s escaped a rerun of The Twilight Zone. Olga pouts and preens, but rarely touches on an emotion that doesn’t feel like a pose. And early on, an elderly male doctor proves so woefully wooden, I was actually cringing.

Yet these bumps of first-time filmmaking don’t detract from Most Beautiful Island’s compelling conclusion. After all that Luciana’s been through, she’s offered a major choice. She can go back to her life of racing around town to nanny for wealthy rugrats and caper for lunch-seeking office workers, or she could return to the warehouse, where she’ll go back knowing her payday means courting death and delving into continued deception to make her American Dream come true. Rather than some strong-worded soliloquy about all she’s seen and learned, Luciana retrieves her backpack from the safety of a trash can, and buys an ice cream cone as she strolls into the sunset. And we’re left to wonder what this means, and who America has demanded this resilient woman become.

Kristy Puchko reviews movies more times on her podcast, Popcorn and Prosecco.

Kristy Puchko is the film editor of Pajiba. You can follow her on Twitter.