The minds of math and science geniuses have long fascinated the makers of crowd-pleasing narrative features, which is curious, as the complexities that fascinate those minds are antithetical to the feelings-first bounce of popular filmmaking. The movies, having settled into candied naturalism, already struggle to suggest interiority, even of characters whose drift of thought is simple — how, then, to lay bare for us the step-by-step breakthroughs of an autistic kid solving an equation?

In his superior British drama A Brilliant Young Mind, director Morgan Matthews (a documentarian making his fiction-film debut) endeavors to show us something of what synesthesia might feel like. Nathan (Hugo's Asa Butterfield), a teen math whiz, stares at wafer-flat street lights that haze and swim over restless, disorienting imagery, some really there before him and some edging in from elsewhere in the brain. You'll likely tense up, knowing that if the kid drifts off, something awful might happen. That's about the only fresh technique the filmmakers invent — otherwise, they leave the mysteries of the brain to their actors, which is probably just as well. When Nathan stands before his math-genius peers, grooving through a theoretical problem, Butterfield's performance is enough — Lord knows we don't need the camera to spin around his head to tell us he's thinking.

So, unlike its hero, A Brilliant Young Mind can't convincingly show its work. (Late in the movie, Nathan's coach says his equation-solving has “rare beauty” but is “unpredictable” and somewhat baroque, all of which comes as news.) But the kind of drama that movies are good at is very good here indeed. Butterfield plays Nathan as brusque and shy, incapable at first of opening up to the world or to the mother (Sally Hawkins) who lives in awed fear of him — she apologizes, relentlessly, anytime she seems to have bugged him, and her voice frays into a ragged toughness as she orders Chinese food for him: The kid needs his meal's menu number to be a prime, and it must have exactly nine prawns — he connects with numbers, not people, especially since the death of his father some years before.

Hawkins is often wonderful on screen, even in this year's slight Paddington, but this performance is a triumph of small gradations of articulated feeling — every fear, every hope, every pain lights across her face, even as the character tries to stanch it all, to reveal nothing more than warmth and her eagerness to love. That eagerness isn't just directed toward Nathan. In the film's most surprising and delicate scenes, Hawkins' Julie finds herself eager to spend time with Nathan's math mentor, Mr. Humphreys (Rafe Spall), a once-promising mathematician who is charming, embittered and living with multiple sclerosis. These are the finest scenes of adult courtship this side of Blythe Danner and Sam Elliott in I'll See You in My Dreams — and just as in that small marvel of a film, the complications these grown-ups face feel like the grinding of the world rather than the delay tactics of screenwriters.

Nathan, meanwhile, makes the United Kingdom's squad in the International Mathematics Olympiad, winning himself a trip to Taipei with kids like him from around the world — and the romantic interest of the first young women he's ever met whose thinking resembles his.

The film is novel-rich, so bristling with life that you might not notice how familiar it is in its contours: Here's the young genius entering a major competition whose final contest comes not long before the credits roll; here's the troubled young man learning to open up and maybe even love; here are awkward first kisses and a mentor with something to prove to the world. But nothing here works out the way it usually does on screen, with that one gently disappointing exception: The filmmakers here illuminate something of what it's like to live and grow but little of what it's like to inhabit a mind likely quite different from yours.

A BRILLIANT YOUNG MIND | Directed by Morgan Matthews | Written by James Graham | Samuel Goldwyn Films | Landmark

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