For all its inclusion of raunchy dialogue, seriocomic carnality, and oral sex (implied to be happening beneath a strategically placed bedsheet), there is something oddly quaint about “The Unicorn,” director Robert Schwartzman’s lightly amusing trifle about two long-engaged millennials who contemplate a walk on the wild side — specifically, a threesome with another man or woman — before forging marital ties.

In terms of structure, predictability, and ultimate payoff, the film resembles nothing so much as the formulaic risqué farces that once provided gainful employment for faded TV and movie stars in dinner theaters decades ago. (Think Neil Simon’s “Last of the Red Hot Lovers,” only broader and smirkier.) On the plus side, however, lead players Lauren Lapkus and co-scripter Nick Rutherford are amply engaging and sympathetic, even when the behavior of their characters is cringe-worthy embarrassing. No, never mind: Make that especially when those characters are humiliating themselves for our enjoyment.

Malory (Lapkus) and Caleb (Rutherford) — or, as they call each other, Mal and Cal — begin to slip-slide out of their comfort zone during a trip to Palm Springs, where they are happy to help celebrate the 25th anniversary of her parents (Beverly D’Angelo and John Kapelos), but considerably less pleased to hear her mom’s encouragements to finally put a ring on it after their four-year engagement. Their uneasiness abruptly spikes when they discover what her parents credit as the key to a happy marriage: occasional romps with a discrete, flexible, and enthusiastic third party (aka “a unicorn”). The more they think about it, though, the quicker their discomfort gives way to curiosity.

Working from a screenplay that Rutherford, Kirk C. Johnson, and Will Elliott based on his own original story, Schwartzman sustains a satisfyingly brisk momentum, but allows his two leads sufficient time to pull off the comic equivalent of a slow-burn during the build-up scenes. Mal and Cal are at once mutually deferential (“I could be cool with this if you are cool with this!”) and increasingly excited as they chart their course across unfamiliar waters. And they struggle, with mixed success, to maintain some semblance of equilibrium, or at least some shards of dignity, after they start to flail about in the deep end of the pool.

Of course, since there is traditionally an iron-clad guarantee in scenarios such as this that desires will be frustrated and misbehavior will never get entirely out of hand, it’s not exactly surprising that Mal and Cal are hard-pressed to successfully lasso a unicorn. Their first close encounter, with a provocatively dressed New Ager named Jesse (a sprightly and sensual Lucy Hale), ends with a disastrous misreading of mixed signals. Round two is a split decision: The couple edges close to connecting with Tyson (Beck Bennett of “Saturday Night Live”), the polysexual bouncer at a gay strip club, until one of them notices — or imagines? — the other’s discomfort.

And just when it looks like they’ll get third-time lucky with April (Dree Hemingway), a “message therapist” willing to work undercover, the flesh is initially willing, but the spirit weakly deflates. Additional complications follow, as a past escapade is referenced just long enough to cause a dramatic rupture before being quickly and entirely forgotten. Which, again, is par for the course in this brand of contrived comedy.

(There may be a reason why Schwartzman underscores many scenes with what sounds like Muzak suitable for a Hawaiian-themed restaurant, but that reason is not readily apparent.)

Throughout most of “The Unicorn,” the dialogue consists largely of anxious and/or animated character-defining quips that Lapkus and Rutherford nimbly toss back and forth like partners in a tennis match or a juggling act. Mal comes across as by far the more level-headed and comfortable-in-her-skin of the pair, while Cal repeatedly seems strained by the sheer effort it takes to talk his way through his insecurities. They may not be the perfect couple, but they are perfect for this movie. On the other hand: The ambiguous final shot, highly reminiscent of a similar image at the end of a classic 1967 comedy, strongly indicates that we shouldn’t make rash assumptions regarding what the future has in store for them.

Film Review: ‘The Unicorn’

Reviewed online, Houston, Jan. 28, 2019. (In SXSW Film Festival.) Running time: 89 MIN.

  • Production: A The Orchard release of a Beachwood Park Films production. Producers: Russell Wayne Groves, Robert Schwartzman. Executive producer: Bret Disend, Jessica James, Mark Weiss, Al Di, Bo An, Viola Du, Nick Gross.
  • Crew: Director: Robert Schwartzman. Screenplay: Nick Rutherford, Kirk C. Johnson, Will Elliott; story: Schwartzman. Camera (color): John Schwartzman, Michael Rizzi. Editor: Chris Donlon. Music: Michelle Johnson.
  • With: Lauren Lapkus, Nick Rutherford, Lucy Hale, Beck Bennett, Dree Hemingway, Darrell Britt-Gibson, Maya Kazan, John Kapelos, Beverly D’Angelo, Kyle Mooney.