Heaven Knows What opens with a suicide attempt. Harley (Arielle Holmes), a young heroin user, offers to kill herself as an apology for cheating on her boyfriend Ilya (Caleb Landry Jones), and when he rebuffs her attempts at reconciliation, she slits her wrists in a public park. She doesn’t die, so he doesn’t forgive her, and their doomed romance goes on in this raw, tender, and altogether mesmerizing new film.

Of course, every junkie (or fan of drug dramas) is painfully familiar with the dynamic of a destined-to-fail relationship. An addict’s first love, these films tell us, will always be the high. Either she quits using, or the drug kills her. Heaven Knows What is no exception. Its story of young heroin users struggling to score and survive on the Upper West Side never threatens to force a happy ending, but the brilliant and fascinating lead performance by Holmes will keep you rooting for one anyway.

With her quiet confidence and conventional good looks, Harley is quickly identifiable as a runaway, a middle-class girl who has traded the trappings of suburbia for a dangerous life on the streets. She has become part of a loose-knit community of junkies who meet up every day to shoot up and goof off. In between, they drink, steal, and sometimes fall in love. Harley used to be with the cruel and charismatic Ilya, but now dates the more down-to-earth Mike (played by the magnificently named Buddy Duress). Ilya, meanwhile, shows up from time to time like a ticking time bomb, threatening to destroy her fragile romance and possibly her life. It’s a dangerous and desperate love triangle that seems sure to end in tragedy.

As compelling as the film is, the story behind it might be even more amazing: Filmmaking brothers Benny and Josh Safdie were working on another project when they spotted Holmes entering the subway. They introduced themselves and learned about her semi-homeless existence as a drug user on the streets of Manhattan. The brothers encouraged her to write down her experiences; she eventually published a book. A couple of years later, Holmes is the star of her own story.

A background like that would threaten to overtake some films, but the Safdie brothers use it to their advantage, capturing the raw emotion and physical danger of Harley’s existence with a brave commitment to verisimilitude. Like many low-budget indie dramas, Heaven Knows What employs the visual style of cinéma vérité—there’s lots of shaky, handheld camera work and a loose narrative style—but it also embodies the movement’s quest for realism more than any other film in recent memory. The Safdies cast real-life addicts in most of the key roles, which should in no way diminish their acting accomplishments. Try just being yourself onscreen sometimes, and see how that goes.

And yet the few directorial flourishes the Safdies do add elevate Heaven Knows What from a competent indie to a near masterpiece. Consider the prominent electronic score: At first, it feels out place in the film’s otherwise gritty realism. Eventually, it starts to make sense, pulsing through the scenery, embodying the anxiety of a junkie looking for her next fix. Careful listeners will notice an updated version of Debussy’s “Clair de Lune” in several scenes, which keenly raises the struggle of these lowly characters to a more profound plane. Like so many urban dwellers, they are stuck in eternal moonlight.

Heaven Knows What opens June 12 at Angelika Pop-Up.