There’s a moment in The Good One, writer-director India Donaldson’s fantastic debut feature, that is so perfectly chosen it took my breath away. The film’s emotional fulcrum is a casual, almost offhand line of dialogue in which a crucial trust is broken and our young heroine gets a rude introduction to the adult world. That line will impact the rest of the film, and presumably the rest of these characters’ lives. But Donaldson doesn’t overdo it, forgoing the expected melodramatic musical interludes or over-the-top reaction shots. She simply keeps the camera focused on star Lily Collias’ face, half-obscured by campfire light, as she silently processes what just happened.

Watching the scene from my couch during the online portion of the Sundance Film Festival last January, I marveled at how easy it is for audiences at home—especially critics, who seem to spend half the running time of their festival screeners posting on social media—to miss this moment entirely. But when I rewatched “Good One” at this year’s Independent Film Festival Boston, the audience in the Brattle Theater was so rapt and rapt that a woman behind me actually gasped “Oh no!” when it happened. It’s a common misconception that the big screen is for spectacular movies, and that intimate dramas like Donaldson’s film can be watched at home without missing much. But I’d argue that small films like this benefit even more from the focus and attention you can muster when the only light in the room comes from the story you’re watching.

“The Good One” rewards such an investment. The film may be modest in scope, but not in ambition or impact. The deceptively simple story sends Collias’ 17-year-old Sam on a weekend camping trip in the Catskills with her irritable, controlling father, Chris (James Le Gros), and his shuffling wreck of a best friend, Matt (Danny McCarthy). Matt’s son Dylan — a childhood playmate of Sam’s — was supposed to come on the trip, but canceled after another argument with his father. Matt’s recent infidelity has torn the family apart, a situation Sam knows all too well, given her own father’s past transgressions. Now forced to act as referee and chaperone for two lost middle-aged boys, she occasionally calls her friend (Sumaya Bouhbal) and wonders how she ended up on this trip.

There’s a version of this film that’s easy to imagine as awful, and since Sundance I’ve had trouble explaining it to friends, wary of painting a picture of the wise and all-knowing Gen Z lesbian brushing off some old-fashioned macho braggarts in the woods. The Good One is a far more complicated and sensitive film than that, and I find it telling that Donaldson, 40, wrote the screenplay partly as a response to becoming a mother herself.

It’s a film that focuses specifically on relationship dynamics, and we get to know these three people pretty quickly. Bearded, boisterous Matt has always been like a funny uncle to Sam, cracking inappropriate jokes to piss off her stuffy father. But now, with his marriage and career in tatters, there’s a heaviness to his humor. McCarthy plays him as a guy who realizes, a few years too late, that his antics are no longer funny. Matt shows up for their grueling hike woefully unprepared, carrying a backpack full of junk food and wearing blue jeans.

It’s clear that he and Sam’s dad lost anything in common sometime after college, but Chris keeps Matt around anyway to make himself feel better about messing up his own life so much. Everyone has that messy friend who makes you feel better by comparison. (If you don’t, that means you’re probably the messy friend. That’s usually me.) It’s a fearlessly unflattering performance from ’90s indie film star Le Gros, who plays the type of guy who views every interaction as some kind of competition, even though no one else is trying to win. Perhaps the most emasculating scene in the film is him trying to outdo a group of well-traveled college kids who can’t possibly see him as a rival.

Donaldson keeps the camera focused on Collia’s face during most of these interactions. This is the actress’ first major role, but she’s already one of the film’s best listeners. We watch her watch them, as a young girl finds her place not only in their dynamic but in the adult world as a whole, where, for better or worse, she’ll have to deal with the same kind of controlling, obnoxious men. Sam has a very funny—if a bit too writerly—monologue about her father having a new baby at 50, but for the most part she’s a thoughtful, reactive presence. And in a captivating way.

Donaldson is the daughter of Australian filmmaker Roger Donaldson, a seasoned journeyman known for powerful thrillers like “Smash Palace” and “No Way Out” (and also for my most shameful secret vice, “Cocktail,” which is the closest thing I’ve ever made to a Tom Cruise Elvis movie). His testosterone-fueled films have little in common with “The Good One,” but clearly shaped its milieu. The most obvious influence is Kelly Reichardt’s “Old Joy,” with its portrayal of a fragile male friendship that runs out of gas on a camping trip. The younger Donaldson has a similar eye for nature and an ear to Reichardt’s for the spaces between lines of dialogue. In interviews, she has spoken of a sense of permission she felt after watching Claire Denis’s “35 Shots of Rum,” another film in which a daughter learns, almost wordlessly, to see her father figure as a person and forges her own path.