06/12/2012 08:17 am ET Updated Aug 12, 2012

Movie Review: Your Sister's Sister

Lynn Shelton had me at Humpday, the feature that introduced me to the intuitively funny filmmaker, who comes back strong with Your Sister's Sister, opening in limited release Friday, June 15.

Working once again with Mark Duplass, Shelton brings Emily Blunt and Rosemarie Dewitt into the mix, in a story of unspoken and unintentional attraction. Shelton's loose, natural approach to acting and scene structure is meant to be instinctive. And Shelton should definitely trust her instincts.

Working from a story that Duplass brought her, Shelton crafted a tale of a guy, grieving over the death of a beloved brother, who accepts the invitation of a close female friend, Iris (Emily Blunt). She gives him the keys to her family's island cabin near Seattle, on the proviso that he go there alone and just unplug in order to deal with his feelings.

He arrives there late, to discover that someone else already is in the cabin -- another family friend, apparently, named Hannah (Dewitt). Once she's convinced that he's not some masher and has a genuine claim to the cabin as well, she lets him stay and they decide to co-exist.

She, as it turns out, is hiding out after a bad breakup with a lesbian lover. She's been involved with men before but has been committed to same-sex relationships for a while.

But the heart is a tricky thing, particularly when combined with a large amount of drink. And, in what they drunkenly agree is strictly a one-time, what-the-hell, spur-of-the-moment thing, they sleep together. After which he discovers that, in fact, Hannah is Iris' half-sister. Which, of course, forces him to focus on the fact that he actually has feelings for Iris.

Shelton has such sharp timing that it's hard to believe that each scene isn't carefully planned, instead of discovered in the moment. As in Humpday, a secret is at the heart of the humor, one that explodes all three lives, if only temporarily.

Shelton also has the outstanding chemistry of Duplass with each of (and both of) these women. Duplass continues to grow on me as an actor; he's already won me as a writer-director. He handles cocky, smart-guy banter better than any actor since Bill Murray in his prime. Blunt has a wonderfully direct quality that is equal parts sympathetic and no-nonsense -- a combination of "Buck up" and "Wise up."

Dewitt shows her claws while exchanging banter with Duplass, playing a woman with at least as hard a shell as he has. This is one of the best roles she's had in a while -- and she's right at home in it.

Your Sister's Sister is smart comedy, such a rarity. It never forces laughs but keeps you steadily and regularly amused.

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