The number of things that Beach Rats does that would ordinarily annoy the hell out of me is basically all of it. And yet. Somehow, the precise ratio of ugly-ass indie film cinematography, meandering narrative focus, and pointedly smudgy adolescent self-discovery is managed by writer-director Eliza Hittman (making her second feature; I have not seen her first, 2013's It Felt Like Love, but it seems that the two films hit several of the same notes) into a gripping whole, an exceptionally satisfying exercise in otherwise unimaginative cinematic realism. Right up until the script makes an enormously misguided shift in the final 20 minutes or so, and practically dares you not to hate it, but let's not go there. We have 70 good minutes to get through, first.

And most of those 70 minutes are trained tightly on the face of Harris Dickinson, an extraordinary find who certainly represents Beach Rats's most emphatic contribution to the annals of film art, Hittman's proficiency notwithstanding. The film largely avoids having anything that really resembles a "plot" - things happen, in chronological order, and later events are caused by earlier events, but the only thing that binds all the events together is the protagonist Frankie, caught in the fuzzy state of being a legal adult but not an emotional one, and not really evolving out of that state during the course of the movie's 95 minutes. That is to say, it's an especially pure character study, one in which drilling into the character's brain is very nearly the only active goal the movie sets for itself.

Dickinson proves splendidly equal to the task; though to be entirely fair, it's a screen performance that comes about entirely through cinematic means: the way that editors Scott Cummings and Joe Murphy cut in the grainy close-ups of the actor's reaction shots, compositing the character out of fragments, all still expressions and muttered line deliveries; and the way that cinematographer Hélène Louvart uses grainy 16mm stock to turn the young man's gorgeous features into the material of harsh realism. The net result of all of this is more an impression of Frankie's psychological state than a clear depiction, which is very much exactly the story that the film is telling: at the time we meet him, Frankie is trying to figure out who he is - trying rather, to squash down who he is, a man who's sexually attracted to other men. And a man who, as the film progresses, starts arranging late-night trysts with older men he meets on a gay chat site, despite his level best attempts to chase hot girls like any other dissolute, jobless Brooklyn working-class 19-year-old.

As a "horrors of the closet" story, Beach Rats covers no ground new in the annals of queer cinema, but I see no reason to hold that against it. It is very distinctly not aiming to be a story of The Gay Male Experience (Hittman is, after all, a straight woman), but a story of the very particular sense of dislocation felt by Frankie, a specific man in a specific place at a specific moment in history (all those '80s gay movies that Beach Rats evokes did, after all, lack the transforming potential of the internet and the film's Chaturbate-like hookup site). That's the wellspring of one of the two main tensions driving Beach Rats, I'd say; the extreme specificity with which Hittman depicts the behavior of poor white bros in the Brooklyn hinterlands, driven to give up the hope of any better life than having a chance to get stoned most nights; the specificity of the several men Frankie meets up with, all of them anonymous fucks, but each of them emerging as a distinct personality even in just a few minutes (there's the skeevy predatory one, the sweet dad-like one, the bashful college kid); the specificity of the gross-looking cinematography, capturing a grotty, wholly unromantic corner of New York that doesn't usually show up in movies, not even movies about the sex lives of young Brooklynites; the specificity of Simone (Madeline Weinstein), Frankie's doomed girlfriend, whose tetchiness and body language tell us volumes about how she feels, even when the screenplay (necessarily) treats her as just an accessory in Frankie's self-negating arc.

All that specificity lies in contrast to the blur of Frankie himself; Dickinson's tightly calibrated performance aside, we don't quite get a sense of who this character is, and that's surely because he isn't; he's an inchoate mass of urges, resisting the process by which they'll be formed into an identity. It's chiefly because of this blurry protagonist that I think I'm so willing to forgive in Beach Rats aesthetic choices I'd rage against anywhere else; the basic simplicity of the film's style mirrors the immature shapelessness of the protagonist.

The other stark contrast fueling the movie is more emotive and experiential: it's the tension between frank eroticism - Hittman isn't squeamish about letting the camera glide over male bodies, at one point giving Frankie a shower scene that, gender-swapped, could have come out of any chintzy '80s horror movie in its unabashed pleasure at leering - and, quite surprisingly I thought, white-knuckle tension. Here's the secret about Beach Rats: deep down in its heart, it's a thriller. This, more than anything, is what having Dickinson and the editors build up the character from reaction shots lends to the movie: the character's shell-shocked looks of panic and fear after he allows himself to sink into the aforementioned eroticism. See-sawing between these emotional extremes ends up pushing Beach Rats along quite nicely, while engendering in the viewer the same sense of horny terror that seems to be Frankie's response to most of the world.

It's all quite impressive and insinuating as a character piece, but it leads perhaps inevitably into the point where the tension finally has to explode. Beach Rats, I've suggested, mostly lacks a plot; the problem is that it should entirely lack a plot. Or, at least, it should lack the plot it ends up with. Far be it from me to spoil things, but let's just say that the film goes dark in a fairly trite way, and one that feels unearned by where we've been before this. It's not untrue to the characters, I suppose, but it's still an intrusion into the very delicate vibe of the movie. A reactionary intrusion, one might even argue, but I don't think we need to go that far to find it disappointingly tone deaf. The end of Beach Rats belongs to a complete different film altogether, one bounded in action and not in passive character psychology. The beginning is good stuff, undoubtedly, but it's not hard to feel ill-used by any narrative that waits till the very end to spring all of its worst ideas on you.