“The One I Love,” with effective and creative performances from its two leads, brings its core concept to a satisfying end.

Ethan (Mark Duplass of “The League”) and Sophie (Elizabeth Moss of “Mad Men”) have reached an impasse in their relationship. Apparently, Ethan cheated on Sophie, and that’s all we know.

They go to couple’s therapy and don’t seem to be getting anywhere, but their therapist (Ted Danson) doesn’t seem to be trying really hard. After a piano-playing compatibility exercise fails, the therapist suggests they spend a weekend away in a picturesque retreat that’s worked wonders for other couples in the past. Ethan and Sophie are both game for a last chance to salvage their marriage.

Spoiling large twists for the viewer should usually be avoided when covering a film. However, the twist in this film comes relatively early and is inherent to the narrative.

Ethan and Sophie arrive at their gorgeous getaway and, while exploring the grounds, come upon a guesthouse.

The twist: It contains the ideal doppelgangers of their respective partners. For example, when Sophie enters the guesthouse alone, waiting for her inside is someone, or something, that looks exactly like Ethan. This Ethan, however, doesn’t wear glasses, has windswept hair and is more emotionally available. The “real” Ethan doesn’t transform into this “better” being — the two are separate entities.

Same scenario goes for Ethan when he enters the guesthouse. He’s met with a Sophie that makes him breakfast and always has a smile on her face.

After some back and forth, the “real” couple decides to test the waters of this surreal cosmic aberration, each taking turns to go into the guesthouse. They set up some ground rules, such as “no getting intimate with the other,” that inevitably gets broken.

The whole situation is a lot to take in, and we’re glad to have Duplass portray Ethan as the one who is most uncomfortable with everything. He mirrors how most of us would probably react. He gets a lot of comedic mileage with incredulous looks at the escalating weirdness around him.

His foil, Sophie, enjoys his doppelganger a little too much.

Director Charlie McDowell and screenwriter Justin Lader turn our preconceived notions of love and identity on their heads.

Even though the supernatural beings in the guesthouse are not the real, physical people they married, they are in spirit: They are Ethan and Sophie before the honeymoon phase wore off, before the spark died out, before it was a burden to be married.

Who wouldn’t want to get that back? They wouldn’t just be someone who reminds you of how things used to be. For all intents and purposes, they’d be the same person you had those experiences with. It’d be a reset button.

Duplass and Moss play two roles apiece and deliver nuanced performances. It’s always a little ambiguous what each person desires.

The third act takes some twists and turns that are not fully explained, probably because the film is incapable of explaining them. It’s not important that we know how the clone couple came into existence, but it still nags at the back of your mind a little.

Nevertheless, “The One I Love” — in large thanks to Duplass, Moss and its concept — is a thought-provoking film with an interesting twist.

Grade: B

—Follow Alex Guyton @GuyTonAlexAnder