“The Baltimorons” is a terrible title for a sweet film. What were director Jay Duplass and co-screenwriter and leading man Michael Strassner thinking? They were likely thinking that it keyed into a segment of the film in which our hero, Cliff (Mr. Strassner), gets on stage and runs through an improv comedy bit that has been a staple of the local scene. Dubbing the local crowd “morons” has its purposes in a raucous club setting, but there are better ways of selling a rom-com, especially one as unexpected as this one.

Then again, Messrs. Duplass and Strassner haven’t brought us a typical rom-com. “Baltimorons” hits the beats to which any devotee of the genre will recognize — the “meet cute” or the sundry volleys in which our protagonists engage before relinquishing their qualms to the blessings of love. The story takes place on the day of Christmas Eve, sneaking a bit into Christmas itself. Presents are bestowed, remonstrances forgiven, and families find joy in each other’s company. Is that the sound of sleigh bells? You get the point.

But then there is a suicide attempt and other unpleasantries, including emergency dental work, breaking and entering, a tenuous sobriety, and the difficulty in locating soft shell crabs during the off-season. Our characters are not standard-issue Hollywood idols: Cliff is unkempt, chubby, and not always as funny as he thinks he is; Dede (Liz Larsen) is a divorced woman of a certain age who radiates an air of been-there, done-that.

From this tangled web is woven a low-key, low-budget, and unassuming love story. Mr. Duplass’s name at the top of the credits prompted wariness from some moviegoers — particularly those who appreciate the finer delicacies of enunciation. Mr. Duplass and his brother Mark are known as the progenitors of “mumblecore,” a subset of contemporary cinema that presumes to take on the cadences of actual conversation through the use of improvisational strategies. When one observer heralded “The Baltimorons” as “an endearing throwback to mumblecore’s heyday,” not a few of us rolled our eyes and hoped for subtitles.

That fear was waylaid as soon as the picture started rolling and, besides, there are welcome facets of mumblecore that are front-and-center, especially a middle-class milieu, documentary-like grit, and narrative apercus that, though absurd, have about them the weight of experience. As a director, Mr. Duplass has a deft touch, forgoing cinematic flash in the grand pursuit of plumbing the complexities and contradictions of his characters — and these are characters worth knowing. 

Our anti-hero, the 30-ish Cliff, is at an important juncture in his life, having become affianced to his long-suffering girlfriend Brittany (Olivia Luccardi) and taking on a daunting set of responsible duties, not least of which is visiting his potential in-laws for brunch on Christmas Eve. Cliff never makes it through the door: He walks smack-dab straight into it and loses a tooth. 

Stemming a tide of blood with an ungainly terry-cloth towel, he calls every dentist in town, finally reaching Didi (Ms. Larsen), a self-admitted workaholic who likes to get down to brass tacks or, in Cliff’s case, a temporary filling. Even at this early stage in the game, Mr. Strassner and Ms. Larsen exhibit considerable chemistry, evincing vulnerability and kindness through a tense back-and-forth.

What happens next is a domino-like shuttling of one damned thing after another, a series of events that bring our unlikely couple closer together. Cliff never makes it to his in-laws, though he does attend the wedding party of Didi’s ex-husband and, in a sop to showbiz predictability, redeems himself as a performer at a pop-up comedy club with Didi as his partner. Predictable, right? 

The thing is, the scene in which our two leads perform “The Baltimorons” sketch is among the most affecting in the movie: Mr. Strassner and Ms. Larsen offer a master class in acting that is subtle and insinuating. If Mr. Duplass lets his movie wander a bit too much after this scene, he soon sets it right and ties up the loose strings in not too strenuous a manner. Here is a gratifying pre-holiday treat.