Starless Dreams is an exercise in pure heartbreak. The documentary has more on its mind than simply making the viewer feel terrible (it is, in fact, a social problem film, though one that offers nothing resembling a solution for the seemingly endless nightmare of human suffering it depicts), but feeling terrible is an unavoidable side effect of the movie's real goal, which is to give voice to the lives and experiences of a group of teenage girls living in a juvenile detention center in Iran.

If that makes it sound even slightly sentimental or cloyingly life-affirming, rest assured that it does not. The young women that filmmaker Mehrdad Oskouei (a most highly-regarded documentarian in Iran, I am told) trains his attention on have not lived pleasant lives, and they have not learned preternatural wisdom from their misery: they have suffered, and for some of them, their suffering has turned them hard, cruel, and proud of their cruelty; for others, suffering has merely robbed them of the ability to feel much beyond a deep sadness that's ready to burst out any time and for a number of different reasons. It has been an ennobling experience for none of them. That's the primary lesson Starless Dreams is on hand to provide, along with a thoroughly devastating portrait of how misery moves in cycles. Most of the girls are in prison on drug-related charges, talking with extraordinary frankness about their histories of addiction; as they reveal their life stories, either in unabashed monologues or dribbled out through numerous evasive appearances onscreen, the common element seems to be that they turned to drugs to escape the savage treatment they've received at the hands of family members or to stave off the feeling of isolation at having been functionally abandoned, and the family members usually prove to be addicts themselves.

The film sketches out a system of mutually reinforcing abuse, in which the young subjects have been so systematically deprived of any tenderness in life that many of them seem almost incapable of understanding what positive, generous emotions even look like. It's not hopeless: we see a one of the teenage prisoners doting over her infant daughter with the kind of love that is, if maybe doomed to being unsustainable in the long term, powerful in the moment, enough so that even the rest of the girls are visible affected. One of the young woman the film devotes the most time to is reunited with her family in a way that strongly suggests that she, at least, will be able to escape the trap that many of the other young prisoners will not. And indeed, the scenes of her quiet triumph are paired with another girl's rising terror at realising that her grandmother has no real intention of taking her back once she's released, over the course of a phone conversation that evolves from cheerful optimism to terrified sobs, in a sequence that is almost impossible to watch, it's so painful and so tightly focused on the simple, literally childlike humanity of the figures within.

It's all too raw for words, and made more so thanks to Oskouei's greatly satisfying filmmaking technique, which brings us into a most intense intimacy with the young girls - uncomfortably so. Oskouei's method seems to have been to ask his interviewees a standard list of questions, some profoundly distressing ("Did anyone ever 'bother' your?" he asks, and I assume "bother" is the translation for some equally sobering euphemism in Farsi; for some girls it means, "sexually molest", for at least one it means "my mother held my arm in an open flame", but not any of them are seen to answer "no"), and some as trivial as "what name would you give your child, if you had one?", which is filtered through some dark worldview even despite being innocuous; one interviewee avers that she'd probably kill a girlchild if she ever gave birth to one, and another subject makes the same statement about a boy, both with guileless looks of calm on their face. Neither one seems to be joking.

In the early going, the film combines these interviews with the detached quality of a direct cinema production, enough to lend the impression that we're watching a sort of Iranian Frederick Wiseman film. As it evolves over its concentrated 76 minutes, it turns into something even richer and more complicated, as they girls start to absorb the presence of Oskouei and his camera, and the filmmaker drifts from being the calm voice with the questions to being obviously concerned and invested in their lives, however much of an academic, journalistic tenor he tries to leave clamped around his throat. This can be charming, as when one of the more boisterous members of the community grabs the boom mike to lead an impromptu karaoke session, or when she and a friend play-act at Oskouei's interview process with a coffee cup microphone. It can be utterly devastating, as when Oskouei is accused of being a chilly outsider who just wants to exploit the prisoners so he has something to show his students. Mostly, it is in between those two extremes, with the director's presence and the young women's obvious awareness of the camera leading them to treat him as a sort of therapist and the lens as a confessional. It is, in the old tradition of '60s cinéma vérité, a movie about the engagement of subject and artist, working together to find emotional reality. It would be so easy for this to turn into exactly that kind of misery porn that Oskouei's accuser fears; instead, what comes across is that this is a collaborative act, with the young women deciding what story they want to tell about themselves, and how they want to use the film to communicate something important about their lives that would otherwise never leave the dingy cement block room and ancient metal bunks of their dormitory.

The results are devastating, in the best way: over the short time we see these people, and their tiny universe, and the regimented regularity that Oskouei captures in repeated camera set-ups and movements, it's hard not to grow deeply invested in their lives, to celebrate the joys that some of them manage to stumble into and weep with frustrated rage at those whose lives will continue through hopeless suffering. It is extraordinarily empathetic filmmaking. Of course, the goal of all movies is to capture a feeling of shared humanity, and to get us invested in the lives and feelings of people who don't exist, or who we'll never meet. But it is a rare and precious experience when a film achieves that as thoroughly as Starless Dreams has; it is an exemplary piece of craftsmanship and a sterling example why documentary filmmaking must exist.