“Every time I wake up, I want to kill or die.” Try to guess the source of that bit of dialogue, and you’ll likely be inclined toward Charles Bronson in one of the umpteen variations of “Death Wish” or, perhaps, a peculiarly nihilistic noir picture made on the cheap circa 1948.

The answer is more mundane and more tragic: Documentary filmmaker Teodora Ana Mihai heard it from a woman named Miriam Rodriguez, whose daughter had been kidnapped by a drug cartel. Why would a Mexican woman of humble means and a certain age confide in a young woman from Romania? “The fact that I was a foreign director,” Ms. Mihai relates, was “the best proof that I didn’t have any hidden agenda that could discredit her.” 

“La Civil” began as a documentary but was turned into a picture “inspired by true events.” The reasons for the shift are aesthetic and existential: Fiction allows for an increase in creative liberty, and the area of Mexico in which Ms. Mihai wanted to film proved too lawless for herself and her crew. Likening “La Civil” to “Death Wish” might, then, seem flip or callous, but Ms. Mihai’s film treads similar ground — that is to say, an exploration of the extreme measures a person will pursue for the cause of justice and family. 

Should you want a comparison less redolent of the grindhouse, think of John Ford’s “The Searchers.” Our heroine, Cielo, is less of a problematic character than John Wayne’s Ethan Edwards, but she’s no less driven and, at the end, equally as isolated. As portrayed by Arcelia Ramírez, Cielo is marked by a determination that is, at moments, shockingly amoral.

The mythic arc of “La Civil,” as well as its emphasis on a lone individual operating within an encompassing landscape, only goes to confirm the commonalities Ms. Mihai’s tale of revenge shares with the Western genre. For parents, though, “La Civil” has to count, above all, as a horror film.

The opening scenes are prosaic and universal. Awash in a golden light, a mother and teenage daughter kibitz in the kitchen, gently ribbing each other in conversation and engaging in making plans. After the young woman leaves for the day, mom gets in the car to run some errands. During her travels, she is abruptly cut off by two gangly young toughs in an SUV. After asking Cielo if she is, in fact, Laura’s mother, they nonchalantly inform her that they have Laura in their possession and a sizable ransom must be paid for her return.

The kidnappers aren’t easily appeased. Cielo, working with her ex-husband (Álvaro Guerrero), scrapes together a payment that falls short of the requested payment. The police prove inefficient, their authority having long been stymied by the ruthlessness of the drug cartels. News reports about dead and decapitated young women being found on a public avenue lead Cielo to an overburdened funeral home. Laura isn’t among the bodies, but Ceilo begins to realize that few people are left untouched by the reach of narco gangsters.

Cielo does her own legwork to find Laura, tailing a host of shady characters and putting herself at significant risk. As a result, her home is vandalized, the car is set afire, and neighbors become wary when not avoiding Cielo altogether. She ultimately joins up with Lamarque (Jorge A. Jiménez), a lieutenant in the local militia who is willing to bend rules and break bones in order to aid the cause. Cielo proves remarkably open to his methodologies.

Ms. Mihai’s experience as a documentary filmmaker is evident in her attention to detail and the manner in which the camera alternately sidles along with, and becomes engulfed in, the events on-hand. Director of photography Marius Panduru casts a generous eye on the natural environs of Mexico, a purview that becomes ironic when his lens settles on some of the country’s more demoralized precincts.

Would that Ms. Mihai’s protagonist was more a flesh-and-blood character than a model of rectitude. Cielo’s lack of affect makes for a hothouse entertainment that remains, in the long run, oddly aloof. The lone moment Cielo comes to life is in the extended final scene, wherein Ms. Ramírez uses all the subtlety at her command to embody a range of conflicting emotions. 

Be warned: The note on which Ms. Mihai’s often-brutal thriller culminates will leave some movie-goers frustrated. Conversely, those who welcome a degree of ambiguity in their cinematic ventures will relish the opportunity to ponder the denouement after leaving the theater. “La Civil” offers much to hash over once the lights have come up.