Justin Kurzel's film takes a rigorously authentic — and suspenseful — look at the roots of a movement that's only grown more dangerously relevant.

There’s a scene in “The Order,” a riveting and explosive docudrama about the dawn of the modern American white-supremacist movement in the 1980s, that creeps you out in a very eye-opening way. Two leaders of the movement are meeting on an isolated country road in Idaho. One of them, Richard Butler (Victor Slezak), is the white nationalist who founded the Aryan Nations, the neo-Nazi cult that has its compound nearby. He’s a racist extremist, but he has the demeanor of a courtly preacher, and he’s consciously political about the growth of his movement.

The other man, Bob Matthews (Nicholas Hoult), is a former follower of Butler’s who has split off from him, all because he thinks the Aryan Nations movement isn’t extreme enough. Matthews wants an armed uprising now, and the insurrectionary band of ruffians he leads, called the Order (he named them after the white-supremacist revolutionaries in “The Turner Diaries”), are basically a small scruffy band of terrorists. They bomb porn theaters and synagogues, they put on black ski masks and tote MAC-10 submachine guns to rob banks and Brink’s trucks. They want the money for themselves, but they’re also funding an “army” to rise up against the United States government. (One Brink’s heist nets them $3.6 million.) In an early scene, we see them kill one of their own in cold blood.

The FBI, led by a dour veteran agent named Terry Husk (Jude Law), has been sniffing around, so Butler is meeting with Matthews to warn him that his violent tactics are a huge mistake. As Butler explains, their movement can’t get bogged down in criminality. If they do it right, he says, within 10 years they’ll have people in the House of Representatives and the Senate. But Matthews won’t listen. He’s committed to his idea of an apocalyptic revolution.

The double-barreled disturbance of the scene is this: Butler, though off by a few years, was exactly right about how the mainstreaming of his movement was going to work. In that sense, he represents a far more dangerous threat to America than Bob Matthews does. Matthews, by contrast, is a reckless sociopath. His string of crimes, which as the movie shows us will culminate in the murder of the Denver-based Jewish talk-radio host Alan Berg (played by Marc Maron), is nothing short of insane. But what that means is that Butler, a seething American Nazi, is the voice of moderation here. That’s enough to make your head spin and your stomach a little queasy.

“The Order,” written by Zach Baylin and directed by Justin Kurzel (whose “Nitram” chillingly dramatized the 1996 Port Arthur massacre in Tasmania), is at once a supremely intelligent docudrama about the rise of the white-supremacist movement and a riveting crime story. Kurzel works in a classical way, shooting the movie (the cinematography is by Adam Arkapaw) with a dynamic feel for the beauty and desolation of the rural mountain landscapes of the Pacific Northwest, and for the moment-to-moment logistics of how amateur criminals move through space. The film is full of robberies, stakeouts, shootouts, interrogations, and other hallmarks of the police procedural. It is, quite often, grippingly suspenseful.

Yet it’s never suspenseful because Kurzel is hyping the action. “The Order” is rigorously detailed in its authenticity. When the FBI, led almost at random into this case (mostly because Husk, the first one onto it, is reeling from a broken marriage and has been assigned to a one-man office in the nothing town of Coeur d’Alene), kicks off its investigation, the Bureau’s tactics, at first, may strike us as a bit sleepy or even borderline inept. But that’s only because the movie is staying true to what the FBI is: a crew of all-too-human agents, not law-enforcement supermen, who in the days before high technology had to move one step at time.

Jude Law, pouchy and downcast, with a weary mustache, plays Terry as an honest agent who is also a broken man (with his wife and two daughters estranged, his job is all that’s holding him together), and this could well be the most searing, lived-in performance of Law’s career. His Terry, who teams up with a local officer (Tye Sheridan, looking as clean-cut as a Boy Scout), is a good cop because he’s full of bitter, hard-won knowledge about how criminals operate. He spent time in New York chasing mobsters, and one of the thoughts he shares — it’s part of the movie’s insight — is that there’s a continuity between members of the Mob, the KKK, and now the Order. The way he puts it is: They all have a cause, but they’re really out for themselves.        

We see that in Nicholas Hoult’s powerfully convincing performance as Bob Matthews. Hoult looks just like the real Matthews, and if the trick in playing a man full of racist hate is not to caricature him — to show us the humanity of everyday evil — the actor brings that off in an utterly disarming way. He shows us that Matthews’ beliefs are total, that he’s living within them, but that they’ve given him a fervor that makes him a scary charismatic thug ringleader.

Matthews turns up in the congregation for one of Butler’s sermons, and when he stands to make his own plea for why the white-power revolution needs to happen now, before it’s too late, Hoult makes us see how righteously he believes that; he sweeps the crowd up into his death cult of ennobling danger. Matthews is actually a rather scurrilous fellow. He and his wife, Debbie (Alison Oliver), have adopted children, but because he wants to carry on his line, he has also impregnated his mistress, Zillah (Odessa Young). He has done it with the same entitlement that, 10 years later, would mark the transgressions of David Koresh. But when Matthews fixes his stare on an enemy, or on one of his followers who he thinks might be disloyal, his eyes shine with a killer’s edge.

Back in the ’80s, Robert Matthews and the Order were big news (Hollywood, in 1988, even made a hamhanded drama about him, called “Betrayed,” starring Tom Berenger and Debra Winger and directed by Costa-Gavras). But as unsettling as the revelations of a neo-Nazi underground were then, few could have guessed what shape the mainstreaming of this movement would take. “The Order,” while scrupulously true to the events of 1983 and 1984, presents itself as a cautionary allegory of what’s happening today: the entwined rise of MAGA and Christian nationalism and the racist dog whistles (and, at times, racist sirens) of Donald Trump’s campaign to take over America. The movie goes into detail about “The Turner Diaries,” the 1978 novel by neo-Nazi William Luther Pierce that became the bible of this movement — it was at once a children’s fable, a handbook of terrorism (with six stages of instruction on how to revolt against the U.S. government), and a piece of hate mythology.

But what “The Order” accomplishes that’s most haunting, and perceptive, is that it shows us how white supremacy in America can be two things at once, two sides of the same coin: the legal and “presentable” side, and the underlying violent side. You can be a hardcore racist without believing that the U.S. government is the enemy. But “The Order” demonstrates that believing the U.S. government is the enemy — which, I would argue, is the cornerstone of Trumpism in the post-January 6, post-Stop the Steal era — is an idea linked, in its emotional and historical legacy, to the ideology of white supremacy. Bob Matthews, as the film shows us at its climax, wound up in a literal inferno for his beliefs. But that doesn’t mean that his ideas burned down.