In an early scene of Until the Light Takes Usa new documentary about the rise of the enigmatic and infamous Scandinavian black metal scene during the last two decadesa pale, beatific man with tattooed arms, a scrappy strap of facial hair and a cascading black mane stares from a train window. He’s bothering no one. Tranquil and reflective, he takes in Norway’s green countryside through the glare of his boxcar opening.

Suddenly, though, the man is standing, retrieving his bags for a calm posse of transportation officials asking to examine their contents. He seems flustered, but not altogether surprised, as if he’s already been through this drill and pondered their blue latex gloves. They’re looking for drugs, he says, but he vows that they won’t find any.

They do find teargas, though. The man, wearing a black T-shirt bearing a Swedish band name that translates as “Fucking System,” or “Shitsystem,” admits it’s his and agrees to pay the requisite fine. They confiscate the gas, and he returns to his seat. The film cuts to the next scene, leaving behind a litany of questions: Why was this man searched when the others on the train, lounging casually, were not? How significant is his fine? How much teargas did he have? Actually, why did he have teargas at all?

During the next 90 minutes of the thankfully subtle, genuinely artful Until the Light Takes Us, we’re offered only suggestions of answers for those questions: The man, for instance, is Gylve “Fenriz” Nagell, the drummer and founder of Norwegian black metal pioneers Darkthrone. In the early ’90s, Darkthrone’s enclave earned international infamy when a series of church burnings, murders and allegations of satanism landed some of the scene’s architects in jail and beneath damning headlines.

“The situation here … has been unpleasant lately,” read a February 1993 newsletter published by Helvete, an Oslo record store that served as that scene’s center, after those incidents turned into fear-of-metal pandemonium. “Attracting reporters, Christians and undercover cops like flies to a corpse.” Though New York filmmakers Audrey Ewell and Aaron Aites don’t explicitly suggest such, it’s logical to assume that Nagell places high on some undisclosed danger-to-the-state list. Again, that’s only a guess.

Appropriately, Until the Light Takes Us asks more questions than it answers about the often misunderstood genre under inquiry. Indeed, beyond a rare collection of interviews with black metal’s surviving deities, Nagell and a then-incarcerated, subsequently freed Varg “Count Grishnackh” Vikernes of the band Burzum, the film’s ultimate achievement might be this sense of open-ended, uncertain inquiry: Why did this strand of heavy metalby then, a major commercial force on multiple continentsbloom in Scandinavia during a span of five years, for instance? How are people on four continents still turning that basic mire into a career? And why has that legacy survived so that, nearly 20 years later, black metal carries an expanding cachet of cool, where nonmetal artists like Sonic Youth’s Thurston Moore and imp-resario Harmony Korine rave (or babble) about it and where documentaries, television specials and books about the scene appear regularly? After all, from the homophobia and anti-Semitism to the racism and American antipathy, how genuine is that scene’s hatred for the rest of the world?

Black metal is an art form that’s willfully shrouded in mystery. The musicians often cover their faces in white-and-black corpse paint, fashioning horns, upside-down crosses and spiky brambles on their skin. Picture lots of leather, blood (some real, some not), chains, nails, knives, tattoos and scars. Only the band namesEmperor, Satyricon, Dissection, Beherit, Mardukand their album namesTransilvanian Hunger, Pure Holocaust, De Mysteriis Dom Sathanasrival the metal musician’s eponyms. For a spell in the early ’90s, the Oslo quartet Mayhem was comprised of musicians called Dead, Euronymous, Hellhammer and Necrobutcher.

And at its best, pure black metal sounds like an artillery blast in a tiny, tiled bathroom. Sonically, it hinges on primitive recordings of very loud guitars that emit sheets of notes rather than one unified melody, drums that pause for very little and vocals comprised of barks, shrieks and incantations. It’s often as impenetrable and irascible as it is exhilarating, churning ahead with the riff-based construction of death metal and the squall of extreme noise and industrial bands. The soundprimal and fierce, largely not commercial and mostly evisceratedoften appeals to those for whom plain heavy metal has simply stopped being heavy enough. In its way, black metal is the ultimate audio drug.

Like that nebulous sound, a lack of clear narrative and fail-safe categories muddles the form’s history. Inspired by relentless bands like Bathory and Venom (who coined the term “black metal” on a 1982 album of the same name), irked by the commercial direction of death metal and the influx of American influence in their city, and bored by the affluence of their socialist enclave, a few Oslo kids started playing an extreme form of metal that flummoxed record labels but quickly found a new audience. It was intense, mean andas Nagell, the man on the train, puts it in Until the Light Takes Usreflects “the painful burden of easy living.” The storyline quickly gets tricky: International acolytes formed almost immediately, even as the Scandinavian scene developed and, in a way, tried to kill itself.

Burzum’s Vikernes, the niche’s ideologue, took to burning churches, while Euronymousblack metal’s mouthpiece and entrepreneursold records to the kids, as if he were a neighborhood narcotics dealer, from Helvete, his dimly lit Oslo shop. Nagell, the survivor on the train two decades later, simply made music and largely avoided the politics and the finances. It’s not surprising, then, that he created some of that moment’s best records (Darkthrone is still making stellar records, butever rebellingthe duo pushes away from black metal now.) Vikernes went to jail, but not before he murdered Euronymous. Dead, the first of them to paint his face white and black, had already committed suicide, and Emperor’s drummer Faust was in jail for killing a supposed homosexual. The facts behind this marathon of death and crime are still disputed by those involved. Some suggest Euronymous murdered Dead, for instance, and we’ll likely never know otherwise.

Those most unsettling aspects of black metalthe murder, the hatred, the destruction of the unwantedwarrants pause. A whole fleet of black metal known as National Socialist Black Metal espouses Nazi slogans and propaganda passionately, while another lambasts as much. Even Nachtmystium, a popular and relatively tame black metal band from Chicago, has publicly made anti-Semitic remarks. In Until the Light Takes Us, Mayhem’s Hellhammer admits he’s proud of Faust, still in prison, for killing a “fucking faggot” who approached him in Lillehammer. Last year, Swedish retro monsters Watain told me in an interview that both Hurricane Katrina’s strike on the Gulf Coast and the World Trade Center attacks were the types of evil they’d like to see perpetuated in the world. Until the Light Takes Us doesn’t dig deeply into these issues, but it always leaves them just at the surface, a subtext meant for the audience to grapple.

That’s fitting, since black metal’s architects have long shirked easy definitions, too, or at least have offered definitions that are at odds with those of their peers. Ask a zealot, “What is black metal?” and you’ve got a better chance at meeting scorn than an answer. The second-wave scene of black metal, which included Nagell and Vikernes, was bound to satanism in the press, though they now deny those ties. Many current black metal bands, however, including Watain, insist that there’s no black metal without satanism. Meanwhile, many black metal acts from other countries, especially the United States, have adopted myriad opposing ideologies: Absu of Texas sings about Babylon and Celts; Wolves in the Throne Room of the Cascade Mountains sings about nature goddesses; Xasthur of California roars mostly about suicide, hatred and nihilism.

But there’s one thing that unites all black metal from hemisphere to hemisphere, decade to decade: It’s intensely personal, unapologetic music that takes one political mode or passion and one furious sound and presents it without reservations. And through all the artful cutaways, elliptical scenes and conscious question marks, that’s the one answer Until the Light Takes Us resounds. This music and this scene matter becauselife and death and profits and freedom be goddamnedit developed an ideology, lived by it, killed by it and died by it. Call them martyrs or call them fools, but black metal’s icons demonstrated commitment and resolve that few artists can claim.

Black metal’s slow metastasis into circles beyond strict metaldom, then, isn’t entirely confounding. In one way, it works a bit like any art that attracts outsiders simply by offering an alternate, alien reality, an escape that they’ll likely never call their own. Gangster rap, for instance, has long given suburban white dandelions a tough, urban fantasyland. J.R.R. Tolkien gave regular blokes infinite vistas of mountains and monsters, wizards and wars. Even something like Mad Men gives a current crop of office loafers insight into a bygone era that they’ll likely never possess: Where those advertising executives were met by bosses who poured tumblers of Stolichnaya vodka and puffed on Cuban cigars during afternoon firesides, the modern worker gets reams of accountability forms and wages that haven’t increased.

Black metal originated in a land of ancient buildings and impressive landscapes, where weather conditions and extreme isolation outside of metropolitan hubs like Oslo worked in concert. Gaahlthe frontman of the black metal band Gorgoroth, who once tortured a trespasser by cutting him so that he bled into a drinking cuptold reporters at his family’s mountainous homestead that he went to school with only one other person until he was 18. In Until the Light Takes Us, Nagell and Varkenes talk about their Norse heritage with great pride. In fact, it’s long been Varkenes’ somewhat reasonable defense for burning Christian churches in Norway, which he deemed as violating the sacrosanct sites of his heritage. After all, they predate the 11th-century Christian conversion of Norway and the ostentatious buildings that followed.

“The appeal of black metal to me in the early ’90s was the fact that it was exotic and such a different muse,” Stephen O’Malley, a prolific American metal experimenter with the bands Sunn O))) and Khanate, recently verified in an interview with me, published in part by Pitchfork Media. “It was my first experience with European culture. … The States is an immediate culture.”

Of course, another litany of questions follows from that justification: Plenty of cultures with ancient cultures make music, so why don’t they too have worldwide followings? Classical grandiosity, African rhythms and Asian and Middle Eastern scales and textures have certainly moved beyond their own borders, too, but Scandinavian black metal was a tiny scene in a relatively small country that lasted for a few years at best? So why is it still gaining prominence?

Perhaps because black metal has teargas, homicide and nocturnal rituals, ordespite the certainty of exposing the poser in us alla landscape of things I’d rather hear about than have. But, again, that’s just a guess.

Until the Light Takes Us screens at Nightlight in Chapel Hill on Thursday, Aug. 20 at 9:30 p.m. Tickets are $9. For more information, visit www.nightlightclub.com or www.blackmetalmovie.com.