To explain the true premise of The One I Love would be to spoil its fun

Since the trailer for The One I Love carefully conceals the film’s unusual premise—a real rarity nowadays, as most trailers are determined to tell the entire story from start to finish—it seems churlish to undo that effort in a review. However, dancing around what’s happening while still addressing strengths and weaknesses will require some fancy footwork. Please forgive the convoluted vagueness that follows.

Here’s what can be safely revealed. Ethan (Mark Duplass) and Sophie (Elisabeth Moss) are a couple whose marriage is on the rocks. The opening scene sees them bickering in a joint therapy session—though sharp-eyed viewers may notice that this scene appears to be multiple scenes, as both characters change clothes and hairstyles from shot to shot. It’s best to just file that away. After failing to get them in sync via traditional means, the therapist (Ted Danson, in a brief cameo) suggests they spend a weekend together at a retreat located a short drive away—just a cozy house with a spacious yard and a guest cottage. Every couple he’s sent there, he claims, has come back feeling renewed. Actually, he omits the word “feeling.” It’s best to just file that away. Ethan and Sophie agree to go, and find the place thoroughly charming, though the tension between them lingers. That is, until they explore the guest cottage, which turns out to have a rather unusual property, provided that only one of them enters the building at any given time.

Written by Justin Lader and directed by Charlie McDowell—both relative neophytes, though McDowell landed a book deal from a Twitter account that pokes fun at two women who live in the apartment above him—The One I Love has a lot of fun exploring the various permutations of that property. There’s an initial suspension-of-disbelief hurdle in that Ethan and Sophie aren’t trapped in their bizarre situation; after initially clearing the hell out in terror, they make a conscious decision to return (spurred mostly by Sophie), which is pretty hard to swallow. Once that’s been accepted, however, it’s easy to enjoy the mounting absurdity (best laugh line: “Is this weird for you now?”) for its own sake, while also admiring the way Lader’s clever screenplay questions what people truly want and expect from their partners. Sophie’s dilemma is particularly poignant, and there’s an underlying sadness to the choice she eventually makes that the film, to its credit, leaves largely unspoken.

If only it had left something else unspoken. Freaky occurrences in fantastic tales are almost always best left mysterious—there’s little to be gained by explaining exactly how people swap bodies, or get transformed from a child into an adult, or whatever the magic may be. It just happens. For a long time, The One I Love looks like it’s sticking to that approach. Toward the end, however, what’s going on in the guest cottage suddenly becomes a lot more specific. This revelation retroactively makes sense of what had seemed like a flaw, which is that Duplass and Moss, at times, give performances that are in completely different registers. (To be maddeningly oblique about it, Moss affects a sort of Stepford Wife persona when Ethan is in the guest house, which is nothing at all like what Duplass does when Sophie is there.) Trouble is, it also raises a ton of practical questions that undermine what had been the film’s primary theme. The ending is intended to be ambiguous, but it’s not too hard to guess what happened in advance, as it’s the only dramatically satisfying option. What’s no longer at all certain is what it means.