It’s impossible to write about “The One I Love” in too great detail for fear of spilling the beans about the major plot device in Justin Lader’s script, though some writers will probably do precisely that and spoil the surprise. Suffice it to say that the initial narrative turn, along with the clever twists that follow from it, proves the major reason why this modestly-budgeted, small-scaled picture, while not without its flaws, is worth seeing.

The film begins with married couple Ethan (Mark Duplass) and Sophie (Elisabeth Moss) consulting a therapist (Ted Danson) about relationship difficulties. After diagnosing them as not being on the same wavelength, he suggests that they spend some time at an isolated retreat where they might recover their passion for one another. It’s a beautiful house on a large estate, and comes equipped with an adjoining guesthouse that becomes the crux of the mysteries that arise during their stay. It appears that the place might be occupied by another couple who could pose a threat to Ethan and Sophie, although what that threat might be will only gradually be revealed.

At one point in “The One I Love,” Ethan mentions “The Twilight Zone,” and it’s an appropriate reference for a story based on a seemingly inexplicable, perhaps supernatural situation. Unlike Rod Serling’s anthology program, however, it doesn’t bother to offer a rational resolution to the circumstance it posits, and that lack might well put off viewers who appreciate not being left hanging. On the other hand, the wooziness of the finale is of a piece with what’s preceded.

One might also point to some modern productions of Mozart’s “Cosi fan tutte,” in which Don Alfonso is portrayed as arranging a swap between the opera’s pairs of lovers because he knows they’re mismatched, as an analogue to what’s going on in Lader’s screenplay. Or perhaps not—one can posit any number of sci-fi explanations instead.

Whatever you decide, though—or whether you decide what the meaning of the movie is at all—the fact remains that once the original set-up is accepted, Lader moves it forward nimbly, and first-time director Charlie McDowell responds with a surprisingly assured follow-through. They’re blessed by utterly committed work from Duplass and Moss, with the former doing most of the heavy lifting but the latter complementing him nicely. Danson contributes a nifty cameo as the therapist whose unusual techniques might conceal a more sinister motive.

Equally important is the technical side of the production. Theresa Guleserian’s production design, Bree Daniel’s costumes and Jennifer Lilly’s editing are elements especially integral to pulling off the picture’s central trick, but Doug Emmett’s cinematography and the score by Danny Bensi and Saunder Jurriaans are also significant to achieving the right overall mood.

“The One I Love” is, however, not only one of those movies one doesn’t want to describe too explicitly for fear of letting the cat out of the bag. It’s also one you don’t want to overpraise and lead people to expect too much of. In many respects it’s a slight piece that, like some of Woody Allen’s films, is predicated on a rather slender, indeed precious, premise. But also like Allen’s best efforts, or like Mozart and Da Ponte in “Cosi,” it uses what initially seems a slight, even ludicrous conceit to treat of deeper relationship issues in an intelligent, sophisticated way. Exactly how it does that is something that should be left to each viewer to discover.

But one can imagine that Serling is looking down on what transpires with a smile.