Ever see how taffy gets made? “Green Room” does something similar with my stomach. As it starts to churn and twist, the end result both nauseates and mesmerizes.

There’s something repulsively beautiful about the savagery at the core of “Green Room,” an early contender for the best film of the year. Writer-director Jeremy Saulnier mixes tension and gore with near-perfect precision, made all the better (and worse, from a different perspective) by the fact that these horrible fates befall characters we actually care about.

Aboard a rinky-dink tour van, a punk rock band called The Ain’t Rights plays three-chord wonders for cheap beer and gas money. And when the funds don’t come through, they steal in order to keep the wheels on the bus going.

However, when a real paying gig comes along, the punks are a little apprehensive. It’s at a white supremacist bar in the middle of the woods, where the clientele adorns themselves with swastikas, Confederate flags and posters that read  “Anti-racist is a code word for anti-white.”

In true confrontational punk fashion, The Ain’t Rights open their set with a cover of the classic Dead Kennedys jam “Nazi Punks Fuck Off.” Although this, shall we say, questionable decision does not register well at first – the band members have to dodge a few bottles chucked at their heads ­– the crowd gradually starts to headbang and slam dance to their own kiss-offs. While approval from racist rednecks is not something to be desired, there’s something commendable about how the ferocity of punk can transcend ideological boundaries.

Unfortunately, everything goes south when the bass player, Pat (Anton Yelchin), walks in on a murder in the green room. The whole band ends up trapped in a building infested with neo-Nazis that plan to kill the group to keep them quiet.

The leader of the white power rabble is Darcy, played by Sir Patrick Stewart. Stewart brings a quiet menace to his performance. While the image of a Third Reich Captain Picard implies ostentatious theatricality, the terror that Darcy evokes comes from his calm, calculating intelligence. Like the eye of a hurricane, he assesses the situation with methodical amorality, and his composure becomes just as disquieting as the maelstrom around him.

The tension of the film is immaculately conceived and unbearable. “Green Room” is a siege film where the only hope of escape is to move forward. Except there lies about 100 obstacles along the way, and everyone knows that not all of their friends will leave unharmed. That knowledge only creates more anxiety for the audience, because we like these punks enough that we don’t want to see any of them reduced to dog fodder.

While The Ain’t Rights may want to emulate their hardcore heroes, they’re too informed by pop culture to actually have a firm grasp of the reality of their situation. They operate on posture and a carefully cultivated sense of authenticity.

When asked by an interviewer early in the film what bands they’d bring with them on a deserted island, they give respectable answers like D.O.A. and Minor Threat. Later, when it becomes clear that they may never see each other alive again, the band members admit they have greater fondness for mainstream acts like Prince and Madonna than they may have let on. Isn’t punk about staying true to oneself? Though Tiger (Callum Turner), the lead singer, maintains that his desert island band was always the Misfits. Have to stick to your principles, after all.

In a vein similar to Saulnier’s previous feature, the excellent revenge thriller “Blue Ruin,” no character is allowed to look cool as they commit violence. The death and bloodshed in this film is ugly and ungraceful. Nobody gets to act like a “badass” in any sense of the word. They go out in the most ignominious ways, and any kills they rack up stem from lucky shots at best. There’s an artful artlessness to the way Saulnier crafts his carnage.

It’s clear at this point that Saulnier is one of the best filmmakers working right now. With the little seen and wildly underappreciated “Murder Party,” “Blue Ruin” and this latest feature, Saulnier is now three-for-three when it comes to violent, morally ambiguous masterpieces.

He has a mastery of pacing: we feel the same dread and exhaustion the punks feel as they fend for survival. He also has a mastery of character: even minor neo-Nazi members that could have easily been turned into faceless grunts feel fleshed out and real.

And he has a mastery of tonal intent: while it’s hard not to cheer when racist skinheads get their brains splattered onto the walls, we still get the sense these confused, angry young men have been misled and manipulated by the charismatic Darcy, and one cannot bask in the moral righteousness of their eradication.

“Green Room” structures itself like a great hardcore punk tune. It’s short, filled with energy and anger and has plenty to say about the chaos it creates. And just like the hardcore scene, the film urges for a sense of community among rebellious, youthful misfits in the face of insurmountable evil. Not everyone may make it out alive, though.

Nate Taskin can be reached at [email protected].