The One I Love is the sort of film that prompts critics to fill their reviews with warnings of spoilers and hammy pronouncements that "to reveal more would spoil the fun." That overstates how tricksy the film is, but Charlie McDowell's debut feature is still a delightful little brainteaser. Ethan (mumblecore stalwart Mark Duplass) and Sophie (Mad Men's Elisabeth Moss) are an unhappily married couple trying to rekindle their passion during a weekend getaway at a countryside house. But after the first night—he pours the red wine adorably, she lights the joint, they giggle and toss grapes into each other's mouths—they realize their memories don't align. Sophie swears they had spectacular sex. Ethan maintains he passed out on the couch. Ethan declares it "some fuckin' weird Twilight Zone shit," but the two decide to flirt with this cosmically aberrant world. That, of course, stirs pain and resentment, but The One I Love never goes full-tilt melodrama. Even as it poses familiar questions—about trust, about the breakdown of communication, about how we alter ourselves for our lovers' benefit—it balances playful charm and eerie tension. Much of the credit goes to Duplass and Moss, who improvised about half of the dialogue and deftly navigate subtle shifts in their performances. Moss, in particular, is a master at ever so slightly tweaking her facial expression to convey emotion, insult and revelation.

Critic's Grade: B+

SEE IT: The One I Love is rated R. It opens Friday at Cinema 21.