One of the pleasures of Sundance – one of the pleasures of filmgoing – is when you know almost nothing about a film beyond title and cast, and then have to take your chances; it’s even better when that film then takes its own chances with its choices. The One I Love, the big-screen debut for director Charlie McDowell and writer Justin Lader, is one of those films – things happen in it that you don’t expect, and even then the unexpected things turn and shift as the film unfolds. But at heart, it’s always about the very real, very complex love between two young marrieds who try to reconnect on a weekend away, and the perspective their getaway gives them.

Ethan (Mark Duplass) and Sophie (Elizabeth Moss) are a young couple – but married long enough to wind up where we first met them, with their smooth and soothing marriage counselor (Ted Danson) trying to talk them through Ethan’s mistakes and Sophie’s resentment. They talk about how they tried to recreate the first night they met — at a party, running out and crashing a stranger’s pool before the home’s owner ran them off — but that the anniversary attempt to recreate it felt forced, flat. “You can’t recapture magic,” Sophie notes. And she’s right. As the twosome go over the same old ground – and yet ache to move forward – eventually their therapist recommends a weekend getaway where they can escape and re-discover each other. He knows just the place; it’s worked magic for many of his other couple-client-customers. And so Ethan and Sophie head North from L.A. seeing if they can once again see what they at first saw in each other …

One of the things that The One I Love understands, and explains near-perfectly, is that every long-term relationship becomes a two-person love triangle – you, your partner, and the better version of you your partner knows you can, and could, be. And that last figure is infuriating, incredibly difficult to compete with. Both Moss and Duplass get to do big things in their performances here – strained arguments, big discussions, sly conversation – but they also get to, and have to, do small things that gradually accrue into unstoppable moments, like a delicate snowfall of individual gorgeous flakes that accumulates to the critical mass of an avalanche. Both of them are terrific in roles that expand and alter as the film moves, like any romance, into places as fascinating as they are truly unexpected.

Considering that The One I Love only has three to four scenes that take place outside of the couple’s romantic retreat, it’s to the filmmaker’s credit that the film never feels claustrophobic or repetitive. And while some of the elements in The One I Love have to be taken with an ounce of faith or a willingness to accept mystery, It’s worth noting that love, like all miracles and wonders, is one of those things you can over-elaborate to death; I’d much rather have McDowell and Lader’s lighter touch than the alternative of a heavy hand. A smart, heartfelt look at the challenges of love, life and what we do when we are not our best possible selves, The One I Love is a magic trick of a romance with nothing up its sleeve and yet a heart worn entirely on it.