Ethan (Mark Duplass) and Sophie (Elisabeth Moss) are trying to recreate their magical first night together – a hazy, dreamy mish-mash of meeting up, finding a spark, and indulging in a little bit of criminal trespassing, all in the space of just an hour – in an attempt to reignite the passion they once felt for each other and their relationship. Charlie McDowell’s deeply smart “The One I Love” opens with Ethan telling us (or, as we soon learn, telling their marriage counselor) about breaking into a stranger’s backyard for a midnight swim alongside his now-wife Sophie, the very thing they did the first night they met. Of course, on that particular night, the owner of said pool was home and caught the duo canoodling by midnight and kicked them out, thus kickstarting a strange need for the couple of have a bit of outsized drama in their romance.

That drama isn’t there anymore, and when the couple tries to recapture it, no one is home – literally, the guy isn’t home – and the pair spends some mystified minutes bobbing in the pool, waiting for something to happen. It doesn’t.

Apparently inspired by his patients’ need to do something to save their floundering marriage, Ethan and Sophie’s therapist (played by an exceedingly wry Ted Danson) asks them to attend a kind of marriage retreat, a weekend away at a beautiful and somewhat isolated estate where they can connect (just the two of them!) and restart their relationship. Fractured by Ethan’s previous infidelity and Sophie’s stubbornness, the pair agrees to the weekend and whatever it may hold. And, no, they are not prepared for what the weekend actually has in store for them.

Justin Lader’s confident and clever script is packed with apparent twists and turns, the kind that make “The One I Love” very entertaining and compelling to watch, but incredibly difficult to write about. Suffice it to say, Ethan and Sophie encounter something at their weekend retreat that is unexpected, bizarre, and essential to the salvation of their marriage. It’s not a murderer hiding amongst the grounds, the film does not turn into some kind of standard home invasion thriller, and there’s not a drop of blood spilled, but “The One I Love” is still tense and somewhat eerie, even as its suffused with charm to spare. Something happens over the course of the weekend, and McDowell and Lader’s clear interest in letting it unfold in a surprising manner is a big part of the film’s amusement and drama. It’s a film of dualisms, of twin natures, of ever-flipping coins.

Twists and turns aside, “The One I Love” confidently addresses some of the biggest questions any romantic relationship can get hung up on – namely, can you become the best idealized version of yourself in order to please your mate? Would you even want to? And what does that mean for your personal well-being? – in an entertaining and crafty way. The film is brisk, funny, smart, and artful, a strong pairing of high concept and relatable storylines.

Duplass and Moss are both tasked with complex roles, and the duo is expected to turn in different takes on the same character depending on the situation at hand. Moss is particularly good here, conveying significant emotion and insight simply by way of facial expressions and the way her smile turns in a particular way. Duplass is a bit more jumped up, and while his work isn’t as refined as Moss’, it’s compelling in a different (and suitable) way that matches the demands of the film itself.

Limited to a handful of locations and primarily set in two houses just a stone’s throw from each other, McDowell’s film never feels claustrophobic or confining, though it is bogged down by an often overbearing score from Danny Bensi and Saunder Jurriaans that too frequently tries to steer the tone of the feature. Overwhelmingly plucky and plinky and zippy and noodly, the music of the film distracts from the crafty stuff that’s otherwise occurring, smart stuff that doesn’t necessarily need aural accompaniment to drive it.

“The One I Love” is a tightly constructed and cleverly designed take on the modern love story, and even if its apparent twists and ever-evolving nature make it hard to discuss beyond broad bits, it’s still the Sundance feature that everyone should be talking about long after the festival closes.

SCORE: 8.8 / 10