On TV and in the movies, Marc Maron almost always looks like he woke up late, hastily threw on the same clothes he was wearing the night before, raced to the set, waved off the hair and makeup people, found his mark and eased into his character.

This is not a criticism. This is a statement of admiration for Maron’s low-key, seemingly effortless and authentic on-screen persona.

Even when Maron is playing someone who is the saddest and most cynical person in the room (and maybe the whole town), he is a brilliant reactor who delivers pithy comebacks and wry observations with pitch-perfect timing.

Sword of Trust: 3.5 out of 4 CST_ CST_ CST_ CST_ CST_ CST_ CST_ CST_ IFC Films presents a film directed by Lynn Shelton and written by Shelton and Mike O’Brien. Rated R (for language throughout). Running time: 89 minutes. Opens Friday at the Music Box Theatre.

These tools are put to great use in “Sword of Trust,” as Maron turns in one of the best performances of his career.

Maron plays Mel, a recovering drug addict and failed musician from New Mexico (and then New York) who has landed in Birmingham, Alabama, as the owner-operator of a pawn shop that’s nothing like those snazzy, brightly shining pawn shops you see on the “reality” TV shows.

This is a place where small dreams come to die. This is a place where a woman forks over $380 to retrieve her fur coat, where a used porcelain creamer is tagged at $15, where a guy comes in with a department store guitar and a pair of slightly worn boots and is happy to take $100 total.

And this is the place where a woman named Cynthia and her partner Mary arrive with a Union general’s sword and a VERY wobbly story about how this sword is a key piece of evidence that will help to prove the South actually won the Civil War.

That item becomes the classic MacGuffin in director and co-writer Lynn Shelton’s whimsical, sharply observed, sweet-natured and very funny “Sword of Trust.”

Clocking in at a breezy 89 minutes, this is one of those slice-of-life character studies where every conversation sounds plausible, even when the content grows increasingly absurd, e.g., when one character says she saw her first ghost just last week, another responds by applauding her for embracing unconventional thinking and proceeds to share his firm belief the Earth isn’t round.

When Mel explains how he wound up in Birmingham, when Cynthia and Mary tell the story of how they met, we can picture every detail they share. We believe they’ve lived real lives.

Jillian Bell plays Cynthia and Michaela Watkins plays Mary, her partner of some 4 ½ years. (Typically stellar performances by both.) They have arrived in Birmingham to tend to business after the death of Cynthia’s grandfather.

Cynthia learns she won’t be getting the house. The bank owns the house, because grandpa had to take out a reverse mortgage to pay for his medical care in his final years. (This is the first of many social/political commentaries, some more subtle than others, about the state of life in present-day America.)

Ah, but Cynthia HAS inherited that aforementioned sword, which comes with a “certificate of authenticity,” a crude drawing depicting the moment the sword was surrendered, and a rambling letter from her grandfather filled with inconsistencies.

Mel believes the sword is authentic but the story is pure and unfiltered B.S. He’ll pay $400 for it. Cynthia and Mary reject the offer and walk out, and that’s that — until Mel’s daffy assistant Nathaniel (Jon Bass), the aforementioned Flat Earther who’s a big fan of conspiracy theorist videos, finds a website operated by Civil War truthers who believe the South actually won the Civil War. (The website even features that same stupid drawing of a Northern general surrendering his sword.)

These numbskulls, who call themselves the Invictusians, are offering five-figure sums for historical items that will help prove their theory.

“What is this, ‘Antique Roadshow’ for racists?” says Mel.

Mel strikes a 50/50 deal with Cynthia and Mary to sell the sword to this mysterious organization — a decision that leads to increasingly complicated and perhaps even life-threatening situations, as they find themselves caught up in a kind of parallel universe populated by ridiculous but also potentially dangerous truthers who are consumed by their ignorance and their bigotry, and feel threatened by anyone that doesn’t look like them and sound like them.

The great character actor Dan Bakkedahl (the foul-mouthed senator on “Veep”) provides comedic spark as a wealthy Tennessee gentleman farmer who’s offering $40,000 for the sword. In the film’s most emotionally impactful scene, director Shelton is heartbreakingly good as Mel’s ex (and former partner in addiction), Deirdre, who shows up at the pawn shop and spins a story about things are looking up for her, really they are — but we can hear the desperation and sadness in her voice, and we can see the pain in Mel’s eyes as he tries to keep his resolve to resist even the smallest step in the direction of returning to the life he had with Deirdre.

In the home stretch, “Sword of Trust” takes on an almost farcical tone that is much broader than the general overall tone of the film. Some of the developments seem a bit rushed and forced, but then Shelton wraps up the story with the perfect grace note, and we find ourselves thinking about the lives of these characters beyond the closing credits and hoping they’re all going to be just fine.