When The One I Love was getting set for release, its star, Elisabeth Moss, was making the rounds of the talk show circuit. I caught one of her appearances, I forget which show, and she was cagey about the plot. She was concerned about giving away the big spoiler in the film. The trailer, having gone through the hands of a marketing department, does everything short of spoiling the big reveal. In the trailer, a troubled couple, Ethan and Sophie (Mark Duplass and Moss), take a weekend retreat to one of those gorgeous houses that so many dream of, and only a few have. There’s a guesthouse on property, and something weird is going on inside. Throughout the trailer, the idea that something is going on inside that house is pounded home again and again and again. Okay, we get it! There’s a unique plot twist ahead and you don’t want to tell us potential viewers what it is, but calling so much attention to it makes you seem desperate for viewers. I hate the trailer for this movie. It crows at the audience like a child on a diving board, calling out for mom or dad to watch the sick cannonball they’re about to do. Just jump in the pool, kid. Mommy is having a grownup conversation.
Many reviewers have cooperated with the filmmakers’ desire for secrecy surrounding the plot, but one need go no further than the internet for spoilers. For my part, I do not feel I can write about this film honestly while avoiding the plot like it’s a land mine. So, if you are a reader who wishes to go into this film ignorant, I leave you with this: The One I Love is a good film. Go ahead and watch it free from any concern that you are about to encounter a stinker. If you have been 
poisoned by the awful trailer, the reveal may not live up to your expectations, but I doubt you will have predicted ahead of time what’s going on in the guesthouse.
For those of you who have stuck around, here come the spoilers.
The guesthouse is not empty. When one of the couple, either Ethan or Sophie, enters the house, a double of their significant other seems to appear out of nowhere. For example, if Sophie enters the guesthouse, leaving Ethan back at the main house, another Ethan all of a sudden appears from the bedroom or the bathroom, and this Ethan is everything that the other Ethan is not, and vice versa. The doubles seem to be a manifestation of all the good things that Ethan and Sophie like about each other. Gone are the little things that chip away at the edges of a relationship, or the things grown so big that they can no longer be ignored. If a person is in the guesthouse, the significant other they encounter is almost a fantasy version, a phantom from the early days of love when no wrong could be done and no slights proffered. It is left to the denouement to reveal the origins of these others, but a viewer’s first instincts is to think of the others as a concrete reminder that no matter what has happened in the relationship, no matter what damage may have been done, there is love still present. Look beyond the troubles, begin anew.
Is it technology? Is it supernatural? To the film’s credit, the answer is not given fully. There is still a fair amount of ambiguity left as the credits roll, but that is not a failing. Director Charlie McDowell and screenwriter Justin Lader have crafted a film that gets the wheels turning, and they do not stop after the experience is over. It’s science fiction levels of audience manipulation in a film mistakenly touted as a romantic comedy. It is a romance, to a point, but comedic? No. It is a relationship story where the protagonists encounter something bizarre and unknown. The focus of the film always remains on Ethan and Sophie even as they become preoccupied with the guesthouse.
As their preoccupation progresses, instead of coming together, as seems the intention of the others in the guesthouse, rifts begin to form, and that is when the film takes off. Ethan and Sophie, like all real couples, have genuine issues that maybe do not respond well to fantasy. Moss and Duplass are perfect for their roles as middle class Gen X-ers whose lives are threatening to unravel. But it is Moss who does the best job. Her character is deeply wounded and vulnerable, but rather than turning defensive and suspicious, she is the one willing to embrace the strangeness, to the detriment of both her and Ethan. Moss was a total pro.
I do not think it was necessary to hide the twist from potential viewers. I don’t think it would change a person’s perception of the film, simply because the reveal is not a jaw dropper. It’s interesting, it’s engaging, it’s unique, but that’s it. If only all films were interesting, engaging, and unique.