The Pororoca, for those not up to speed on their Amazonian geography, is a vast tidal bore that can travel up to 500 miles inland on the great South American river, its waves gathering considerable height and momentum as they move upstream. That might seem an extraneous fact, given that the eponymous natural phenomenon is neither featured nor mentioned at any point in Romanian director Constantin Popescu’s cryptically titled third feature — but “Pororoca” is a simmering, gradually harrowing film heavy on incidental information at the frayed edges of its drama. It’s for viewers to figure out how things fit, or don’t, into its shattered portrait of a family man undone by his daughter’s unexplained disappearance, as his rage and grief accumulate their own destructive tidal force. The Romanian New Wave has never seemed quite so bluntly apt a term.

Premiering in competition at San Sebastian, this is muscular hard-art fare that, with a fair wind and following sea on the festival circuit, could propel Popescu into the upper ranks of his country’s auteurs — among them Cristian Mungiu, one of his co-helmers on 2009’s “Tales from the Golden Age” portmanteau pic, for which Popescu remains better known internationally than either of his previous features. Anyone expecting the darkly droll comic tone of that project, or Popescu’s 2010 sophomore feature “Principles of Life,” from “Pororoca” is in for a stony surprise: Barrelling despair is the dominant emotional tenor in a film likeliest to prompt narrative and tonal comparisons to Andrey Zvyagintsev’s recent Cannes prizewinner “Loveless.” That, combined with the director’s lower profile and a testing (but never tedious) 153-minute runtime, makes “Pororoca” a tough sell to distributors, though probable festival acclaim and awards would help in that regard.

For the opening reels, at least, everything in the Ionescu household seems pretty peachy by the standards of Romanian domestic drama. Banker Tudor (Bogdan Dumitrache) and accountant Cristina (Iulia Lumânare) are happily, jovially married, sharing a spacious apartment in a well-to-do Bucharest suburb with their adorable children, seven-year-old Ilie (Ştefan Răuş) and five-year-old Maria (Adela Mărghidan). To spend some time with the family, however, is to spot a few streaks of malaise: Why is Tudor secretly making violently abusive phone calls to one of his wife’s clients? Is his parenting style sometimes a touch brusque? These are questions that resurface — perhaps irrelevantly, perhaps not — when real crisis hits: One sunny Sunday, Tudor takes the kids to the local park, and while he’s distracted on his cellphone, Maria vanishes from the busy playground.

Popescu stages every parent’s single greatest fear with nerve-chipping specificity and plausibility, Liviu Mărghidan’s hitherto disciplined widescreen lensing going waywardly handheld as Tudor’s panic mounts. Leads are few to none, witnesses are sympathetic but stumped, and the chief investigating officer on the case (Constantin Dogioiu, excellent) is patient but frustratingly dispassionate: Even-handed in its blame and sympathies, “Pororoca” isn’t necessarily the excoriation of Romanian bureaucratic process that this seething national cinema has lately led us to expect, but it’s not hard to see why the police’s guarded approach gradually drives a guilt-fevered Tudor toward rash independent action, particularly once he hatches a pure gut instinct about who his daughter’s abductor might be.

As a more intimate marital study, meanwhile, “Pororoca” may fracture along entirely expected — some might even say inevitable — lines, but that doesn’t make the fallout any less wrenching. Helpless in her agony, Cristina can’t help but blame her husband for his critical, unfixable error; he may ask for forgiveness, but can hardly forgive himself, so what chance does he really have? In one scene of piercing cruelty, Cristina relates exacting details of her daughter’s outfit and morning routine to the officer, while Tudor can relate mere generalities; Cristina’s testimony isn’t intended as point-scoring over her husband, but the longer they mutually brood over the incident, the more irreparably separate their responses to it become. Dumitrache and Lumânare are both quite superb as the drama grinds their characters down to different breaking points: While Cristina struggles to couch her fury in responsible terms, Tudor increasingly surrenders to visceral, primally violent rage.

Popescu makes an disquieting virtue of the ultra-wide frame throughout, particularly as Tudor grows more isolated within it: Each time he returns to the park, as becomes obsessive habit, his daughter’s potential avenues of disappearance stretch out more tauntingly in every direction; later, when stray snapshots from the scene are combed for any conceivable clues, the camera lens’s redefinition of space briefly calls Antonioni’s “Blow-Up” to mind.

Popescu has a knack for staggering multiple lines of tension and conversation in a scene, fleetingly tuning into an assortment of unexplained fringe exchanges and human tableaux: an escalating, absurd altercation between an elderly woman and a dog-walker in the park, for example, or an unidentified woman’s passing grimace of anguish in a police station corridor. As urgent as the driving drama may be, these minor vignettes have a habit of snagging our attention from the central characters’ pain: Glancing away and losing sight of people, after all, is only too easy to do.

Film Review: ‘Pororoca’

Reviewed at San Sebastian Film Festival (Official Selection), Sept. 26, 2017. (Also at RIFF, Zurich, CPH:PIX festivals.)

  • Production: (Romania-France) A Scharf Film, Irrévérence Films production. (International sales: Wide, Paris.) Producer: Liviu Mărghidan. Co-producer: Lissandra Hăulică. CREW: Director, screenplay: Constantin Popescu. Camera (color, widescreen): Liviu Mărghidan. Editor: Corina Stavilă.
  • Crew:
  • With: Bogdan Dumitrache, Iulia Lumânare, Constantin Dogioiu. Adela Mărghidan, Ştefan Răuş, Elvira Deatcu, Ioana Flora, Adina Lucaciu, Emanuel Pârvu, Izabela Neamţu, Dragoş Olaru, Angel Popescu, Mircea Gheorghiu.
  • Music By: