If Trump Derangement Syndrome is real—and let’s see it for what it is: a justified madness at the Administration’s depraved disdain for the norms of democracy and, for that matter, of humanity—there’s also a countervailing artistic alternative, of fury focussed to a sharp point of dramatic precision, as seen in such movies as Spike Lee’s “BlacKkKlansman” and Jim Jarmusch’s “The Dead Don’t Die.” These films, while sparked by the urgencies and the outrages of the moment, insightfully tether them to long-standing and underlying forces in American politics and culture. Add another film to the list: Lynn Shelton’s “Sword of Trust,” which opens in New York theatres on Friday, and both elsewhere and on digital platforms next week.

“Sword of Trust” is a comedic drama of paths, trends, and histories crisscrossing in and around a pawn shop in Birmingham, Alabama. Marc Maron plays Mel, the shop’s dour and grim-witted owner, who’s visited by two new clients, Cynthia (Jillian Bell) and Mary (Michaela Watkins), a couple who’ve recently arrived in Birmingham, to take care of business after the death of Cynthia’s grandfather. There, Cynthia inherits a Civil War sword that’s been passed down from generation to generation, and a rambling and incoherent letter that asserts its historical significance.

Cynthia and Mary want to sell Mel the sword but reject his low offer. Soon thereafter, Mel’s distracted young assistant, Nathaniel (Jon Bass), a master of Internet time-wasting and a consumer of the kooky conspiracy theories that he finds there, discovers an online group of Civil War truthers, Southerners who insist that the South actually won the Civil War and will pay heftily for artifacts—such as swords—that, they think, will prove it. Cynthia, Mary, and Mel, with Nathaniel’s eager help, team up to sell the sword to that group, and get pulled into a dangerous and violent network of hatred.

Shelton, one of the filmmakers who has long been associated with the mumblecore movement, has often relied on her actors’ improvisations on detailed stories of her devising (most famously in “Humpday”), and she does so in “Sword of Trust,” as well. (Joe Swanberg, another of that movement’s key filmmakers, is one of the film’s producers; Maron has acted in several episodes of Swanberg’s Netflix series, “Easy.”) Here, writing the script with Mike O’Brien, Shelton weaves multiple coils of rage into a tense and volatile mechanism that, for all its small-scale action and anecdotal idiosyncrasy, yields bold and surprising implications for politics at large and for modes of resistance. That mechanism is also cleverly assembled, and, perhaps more than any of the recent spoiler-crazed superhero movies, it would be deflating to reveal its most inspired twists, which deliver sheer delight with a theoretical edge. But Shelton also offers the characters a deft shading of backstory that puts the entire plot into high relief and situates it in a wide, complex, and varied civic landscape.

For starters, Shelton makes comedic use of Nathaniel’s obsessive Web-surfing, where the silliness of earnest flat-Earth theorists bleeds into altogether more malevolent delusions of the sort that get the plot moving—and that have immediate and apparent political effects. As a lesbian couple, Cynthia and Mary feel compelled to put on a show of heterosexuality when they meet the sword’s prospective buyers; and when Civil War truthers show up in Mel’s store, their regional and historical prejudices are seen to involve anti-Semitism, as well. While at work, Mel also gets a visit from a woman named Deirdre (played by Shelton); it’s obvious, from their first tense moments, that they’re a former couple, now embittered—and that Deirdre is a former substance abuser whose recovery Mel begins to doubt. It’s a scene that both actors play with an extraordinary, understated poignancy—and that Shelton directs with a precise and dignified restraint. I was surprised that, in crucial beats of the sequence, Shelton holds the camera at length on Mel as he looks at Deirdre up close while gazing far into their shared past with pain and regret; the directorial decision, subordinating melodrama to drama, conveys a sudden emotional crisis and an ethical dilemma.

That relationship, and the life-changing decisions that are entwined with it, emerge in a scene of an operatic splendor when, in a moment of fear-filled pressure, Mel delivers to his trio of cohorts the story of his own life and his relationship with Deirdre in a long and moving aria of love and loss, thwarted dreams and tangled lives, suggesting the vast sediment of hard experience and the tenuous grasp on a daily lifeline that characterize modern American life. It also evokes the complexity of the backgrounds that flow together in that Southern town; “Sword of Trust” is, among other things, a story of ubiquitous migration and cultural variety beneath clichés of local homogeneity.

Yet, alongside its briskly sketched indications of diversity, “Sword of Trust” dashes past many of its other characters, including its one character of color, a black shopkeeper named Jimmy (Al Elliott), who is Mel’s friend and, ultimately, merely a sort of benefactor ex machina. I wish that the movie also offered Cynthia and Mary detailed stories of the scope of Mel’s, too. The movie reaches its conclusion with a deft yet rushed twist that also leaves one of its principal questions completely unexplored—the degree of complicity that the protagonists would bear for selling the sword to those who’d use it to advance political pathologies.

Nonetheless, the movie’s key plot line—the antic yet menacing dive into the conspiratorial Confederate underground—also gives rise to the movie’s most daring observations, ones that echo far beyond the confines of the drama to pose strange and stern challenges to political pieties. No sooner do Mel, Mary, and Cynthia team up to sell the sword than they find themselves facing people who don’t shrink from inflicting bodily harm in pursuit of their goals—and in the face of weaponry, the protagonists depend on weaponry, as well. “Sword of Trust” is, like many classic Hollywood movies set in the old South, a virtual Western and, like classic Westerns, Shelton’s film is centered on aggression and self-defense involving guns. With a seeming wink at John Ford’s great drama “The Man Who Shot Liberty Valance,” “Sword of Trust” shows progressive-minded people forced by circumstances to defend themselves by violent means against cruel and hate-filled people. The crucial matter of the movie is: In a nation where the right wing is armed to the teeth, should the left protect itself by getting armed, too?