An older but still vigorous widow in Recife, a provincial town on the northeast Brazilian coast, refuses to sell her second-floor seaside apartment to an ambitious developer who’s cleared out the rest of the building in Klever Mendonca Filho’s “Aquarius,” an epic-length study of senior determination anchored in Sonia Braga’s ferocious lead performance.

On the basis of that précis, you might expect the film to be a Hallmark Hall of Fame-style heart-tugger, but Filho and Braga treat it in a gritty, realistic way that undercuts such a characterization. The rationale behind the intransigence of Clara (Braga) to give up the home she shared with her husband and children is clearly shown, by flashbacks and a prologue connected with a 1980 birthday celebration for her aunt (Thaia Perez) many years earlier, to arise from the memories about her husband (Daniel Porpino) and family that the place, and the things collected in it over the years, instantly evoke. In the crassest sense, one could write that off as mere nostalgia for the past. As dramatized here, however, it goes far deeper than that: the place represents Clara’s very identity as a person, and losing it would mean a loss of far more than a place to stay.

That’s a reality that Clara cannot make her children, who worry about her safety and in some cases look toward the financial gain that a sale would bring as well, understand. It also comes under increasing challenge as the shark-like grandson of the building’s owner—a smiling business-school graduate named Diego (Humberto Carrao)—employs increasingly threatening techniques of harassment to frighten the woman into accepting his offer. The script connects his actions to endemic corruption in Brazilian society, reaching from private businesses to the highest levels of government, that is willing to sweep away the country’s past—its very identity—to foster crude modernization.

One can fault “Aquarius”—for its length (nearly two-and-a-half hours), for detours into the legal realm (which turn out, in the end, to be diversions, since the resolution comes from admissions by sheepish workers involved in the developer’s shady schemes rather than lawyerly grunt work), and even for a final twist that might be satisfying on a gut level, but on reflection is hardly triumphant, even if it will undoubtedly appeal to local audiences infuriated by the degree of corruption that actually exists in today’s Brazil. One might also criticize the subplot about the young Clara’s (Barbara Colen) successful bout with breast cancer, which, it’s suggested, left her with the ability to soldier through suffering without flinching—perhaps an overly simplistic explanation of her resolve. But Filho’s approach is so direct and sincere, and Braga’s performance so fearless and passionate, that the problems pale into insignificance; even the digressions—Clara’s evening with a widower she meets at a local club, her day out with her nephew Tomas and his girlfriend Julia—add to the texture of the narrative rather than coming across as filler.

The supporting cast is excellent down the line—Carrao is particularly good as the smirking villain of the piece, whom you will size up as quickly as Clara does, but all the players—Zoraide Coleto as Clara’s loyal housekeeper Ladjane; Irandhir Santos as Roberval, a lifeguard who befriends her; Maeve Jinkings as her daughter Ana Paula; Pedro Queiroz as her nephew Tomas and Julia Bernat as Julia, among others—inhabit their parts with unaffected naturalness. Visually the film introduces us to a setting that is both unfamiliar and interesting, and the cinematography by Pedro Sotero and Fabricio Tadeu uses it to fine effect without beautifying it. Clara’s career as a cultural critic allows for the introduction of excerpts from her large collection of LPs, from music by Heitor Villa Lobos to popular songs.

“Aquarius” is a powerful portrait of a resolute woman, and an equally strong assault on the forces of corruption in contemporary Brazil.