The wounds of abandonment and displacement are at the root of Zou Jing’s achingly poetic “A Girl Unknown,” a sober and quietly devastating portrayal of an adolescent girl whose identity, maybe even humanity, has been toyed with by a fractured law. That would be China’s controversial one-child policy, recently interrogated in Nanfu Wang’s stunning documentary “One Child Nation.” While “A Girl Unknown” isn’t directly an examination of the severe initiative that was introduced in 1979 to control the country’s population growth (and formally ended in early 2016, with its additional restrictions terminated in the following years), its harrowing echoes are all over Jing’s story, which spans 12 years, starting in the 1980s.

With many culturally patriarchal families favoring boys over girls as their offspring when challenged by the one-child directive, young girls were disproportionately put up for adoption and forced to exist in a vicious cycle of rejection where they had to survive their dislocation. Among those survivors is Wang Juan (Cao Ruofan), whom we meet as a no-nonsense six-year-old, experiencing the buoyancy of childhood around rural swimming holes and her welcoming, brightly lit school. Like any kid, she gets into trouble from time to time, but this tomboy isn’t the type to suffer any fools or her town’s common bullies.

Things change rapidly for Juan when her mother becomes pregnant, taking her on a long journey to the home of a childless couple: the overly fretting, elegantly styled Ding Meishuang (Shen Jiani) and her irritable, mostly silent husband Wang Weiqiang (Zu Feng), who clearly wants nothing to do with the little girl. It’s evident at once that this arrangement has been made a while ago without Weiqiang’s knowledge. Her mother quietly departs in the morning, leaving Juan behind.

Zou attentively constructs the new chapter of Juan’s life with her new parents, while gradually disclosing the source of the couple’s deeply entrenched trauma and marital strife, too. Zou is especially gifted on the page when establishing the dynamic between Meishuang and Weiqiang, softening the edges of our first impression of them, before pulling the rug from under us by revealing further, grief-soaked complexities to their joint history.

With her cinematographer Liang Zhongqiang, Zou also embraces the vibrant colors and seaside landscapes of Juan’s new, tranquil world, where she settles into a novel routine that includes dance classes, which she aces. A lesser film would perhaps lean into bleaker visuals to accentuate the heartbreaking reality that Juan has found herself in. But Zou’s cinema grasps that unideal truths often can be concealed underneath beautiful surfaces.

As Juan grows up and changes names a number of times in search of an identity that fits her sensibilities, the terrific Li Gengxi (of Bi Gan’s dreamy “Resurrection”) takes over from Cao to portray Juan in her teenage years. Further change is imminent when a different couple shows up out of nowhere to legally claim Juan, now a reclusive young woman who’s fallen victim to a sexual predator. (Zou is sensitive and perceptive in plainly spelling out the assault without actually showing it, keeping the focus on Juan’s survival and perseverance as opposed to the violent act itself.)

The next chapter of Juan’s life unfolds in a clothing factory, where she works for barely any money by day, living at the facility’s grim, overcrowded dormitory by night. Zou’s pacing is gentle and patient as she follows Juan through these ups and downs with compassion, observing the occasional safety and camaraderie she finds in the company of others. Elsewhere, an unspeakable tragedy that befalls a fellow factory worker further establishes the plight of young girls across China’s recent history.

Zou is a skilled and understated stylist in capturing the flavors of the 1990s, via posters that decorate Juan’s wall — “Trainspotting” is especially prominent in that sense — as well as the teenage fashions of the period. If there are occasions where she reaches for cliches (such as heavy-handedly existential underwater shots of Juan) these can be forgiven in an otherwise specific and subtle movie free of formulaic traps.

For a story so tender, so full of misery and human fragility, it feels like an unexpected miracle when “A Girl Unknown” chooses optimism as a parting note. Then again, Zou hints at hope throughout her gradually but effortlessly paced narrative, lingering on fleeting moments of beauty in nature and in art. That in itself feels like a form of rebellion, daring to celebrate the living-and-breathing humanity of those who once felt erased and invisible.