For much of “Boy Erased,” we are watching the face of 19-year-old Jared Eamons. It’s a handsome, intelligent face — it belongs to actor Lucas Hedges — and its range of expressions subtly distills the drama of this somber, coolly appalled and appalling movie.

We note Jared’s dutiful attentiveness as his father preaches a sermon, his furtive downward glance in the company of a boy he likes and his quiet anguish when he finally approaches his parents and disgorges the long-held secret of his homosexuality.

Some time later — or perhaps earlier, given writer/director Joel Edgerton’s deft shuffling of time frames — Jared finds himself at the Christian ex-gay program known as Love in Action, being lectured by the program’s strict director, Victor Sykes (Edgerton).

Hedges’ silent scream of a performance, more internalized than his excellent work in “Manchester by the Sea,” both complements and counters the soul-smothering heaviness of Sykes’ agenda.

The story is based on Garrard Conley’s 2016 memoir about his experience as an Arkansas teenager, when his Baptist parents sent him to gay conversion therapy. The movie’s moral position on gay conversion is clear enough, but to its credit, it seeks to articulate that position without cheap histrionics or easy condemnations, to summon restraint in depicting an ideological campaign that has no particular use for nuance.

Edgerton is a shrewd and attentive filmmaker, as he showed in his underappreciated 2015 psychological thriller, “The Gift.” His knack for evoking domestic tension especially animates the tense, difficult scenes of Jared’s home life after he is outed as gay to his parents under circumstances that constitute their own cruel form of violation.

The parents, Marshall and Nancy, are played by Russell Crowe and Nicole Kidman, who, like Edgerton, conceal their Australian roots in service of a well textured and reasonably convincing snapshot of Southern suburbia. Kidman’s steely grace illuminates the plight of the doting, sympathetic Nancy, who responds to her son’s admission by closing her eyes but not, crucially, her mind or heart. Crowe, meanwhile, conveys Marshall’s natural affection for his son but also his instinctive willingness to suppress it, to bark orders and demand answers in lieu of listening.

That difficult dynamic is replicated, with a much more toxic level of obtuseness, at Love in Action, where Jared is sent after surprisingly little family discussion. From there, “Boy Erased,” shot in dim, muted colors and accompanied by agitated orchestral strings, proceeds with the coolly restrained tension of an art-house horror movie. Or perhaps a prison movie.

As affective as the movie is, it doesn’t fully illuminate one important aspect of Jared’s journey: the spiritual life of its characters. Given its focus on church and community, the movie seems curiously reluctant to broach the subject of God. As a result, it sacrifices a deeper, more intimate kind of insight. “Boy Erased” is a sobering, justly infuriating movie, but its own elisions keep catharsis at bay.