There’s a distant, otherworldly aura to Rebecca Byrne, the teenage protagonist of “ Transamazonia ,” that is quite befitting of someone who literally dropped from the sky. As a small girl, a plane she was on crashed in the remote depths of the Amazon basin, leaving her the only survivor of the tragedy. Hailed by the media as a miracle child, she has since remained where she fell, carving out a reputation in the rainforest as a Christian faith healer. It’s a testament to Helena Zengel ‘s arresting, secretive lead performance that we’re never sure if miracles are Rebecca’s blessing or her branding. This central enigma informs the other, manifold ambiguities of Pia Marais ‘s intriguing environmental fable — in which religious mission work and industrial deforestation both pose threats to Indigenous identity.

Premiering in Locarno's main competition, with a New York Film Festival slot to come, this is a formally powerful and typically thoughtful fourth feature from South African-born writer-director Marais: Her last film — 2013’s simmering character study “Layla Fourie” — may have been set in her homeland, but her career has otherwise been built on a thoroughly international perspective. Postcolonial questions of belonging and displacement play heavily into “Transamazonia,” which is at pains to avoid overly exoticizing the little-portrayed region of Brazil in which it unfolds, securing the collaboration of the Assurini people of the country’s Trocará Indigenous Territory. (They are collectively credited as associate producers.) Still, there’s an opacity to this ambitious, conscientious film’s characterization on all fronts that hinders our emotional involvement, even as it holds our interest.

Rebecca is not alone in her Amazonian sanctuary. Her American missionary father Lawrence (Jeremy Xido), who retrieved her after the crash, seems to have interpreted the tragedy and its location as a kind of spiritual calling. Establishing his own mission in an abandoned Baptist camp in the jungle, he has made Rebecca the star of his unconventional evangelical sermons, attended by Indigenous locals who believe that she has healing powers. If she does, Lawrence’s flamboyant showmanship as a preacher — with the mission’s makeshift interiors bathed in lurid turquoise light — makes them look an awful lot like charlatanism.

Rebecca is a solemn, stoic figure who doesn’t seem intentionally involved in any deception. That’s not to say she is entirely certain about her abilities. Zengel, the remarkable young German actress from “System Crasher” and “News of the World,” portrays a still-traumatized young woman who is uncertain of herself — partly due to normal teenage insecurities and partly because of long-term blind spots carefully cultivated by her father. Nine years after the accident, she knows little about her mother or her family’s past. However, her world is gradually expanding, nurtured by friendships she has formed with other indigenous teenagers, leading her to re-evaluate her own story.

However, at this moment, a great deal hinges on Rebecca’s supposed magical abilities. Alves (Rômulo Braga), the head of a logging company carrying out illegal deforestation in the area, requests her services for his wife, who has fallen into a prolonged coma. The mission is thus drawn into a tense local conflict between the loggers and the local tribes whose land is being threatened — if Rebecca can cure his wife, Alves says, he’ll back down. It’s a situation that reveals the Byrnes’ precarious and uncertain standing in a community that regards them both as outsiders and allies, and raises the question of whether they’re aided or exploited by a mission that provides them with some semblance of spiritual comfort.

“Transamazonia” thus functions as a sort of tense neo-western, with the dense, teeming forest — shot by Mathieu de Montgrand in greens so saturated they sometimes turn to black — serving as the lawless territory of the genre, contested by those to whom it belongs and those to whom, in their minds, everything belongs. The Church’s role in this standoff is up for debate, although Marais’s script (co-written with Willem Drost and Martin Rosefeldt) avoids taking a firm position, observing from a cool distance as these three incompatible groups circle each other. The deforesters clearly represent the enemy, but the film feels otherwise guarded in its sympathies, with the Indigenous characters respectfully but never intimately portrayed.

However, as an atmospheric exercise, “Transamazonia” is tactile and captivating, imbued with the weight of the weather and the restless, chirping sounds. It evokes an environment worth safeguarding, for those who were born into it, and makes you understand how others can lose themselves in it, discarding compasses both geographical and moral. For Lawrence, the Amazon allowed him to reinvent himself; for Rebecca, escaping it might be her rebirth.