Review originally published Jan. 23, 2012 as part of Film.com's 2012 Sundance Film Festival coverage.

"Your Sister's Sister" is exactly the type of indie movie you'd expect to see at Sundance. A few well-known actors, mostly improvised dialogue, and a few weeks to shoot the movie, which it turns out was an advantage.

I hesitate to give too much of the plot away. There are some crucial details you must know about the characters going in, but you really shouldn't know the situations that arise while the movie is happening. The fun here is that the characters continuously catch you by surprise. The improvised dialogue – director Lynn Shelton announced at the Q&A that only about 20 percent of the movie was scripted – leads you through a very natural film experience with real characters in believable situations.

Jack (Mark Duplass) is reeling from the death of his brother. We don't know how his brother died, though we know that Jack is heartbroken because of it. In perfect deadpan Duplass style, Jack doesn't show his emotions. There's a few moments here and there where you can tell he's really hurting, but other than that he puts on a happy facade, attempting to face the day as normal as possible.

Jack's best friend also happens to be his late brother's ex-girlfriend, Iris (Emily Blunt). Iris is concerned about Jack and suggests he take some time off to sort out his life and deal with his feelings about losing his brother. Her family has a secluded cabin by a lake in the woodlands of Washington, so Jack takes her up on the offer. When Jack arrives at the cabin he accidentally runs into Iris's sister, Hannah (Rosemarie DeWitt) who's also staying there. Hannah is trying to get over a life-changing even of her own, she's broken up with her partner and is looking for a little solitude.

These three actors that are the glue that hold the movie together. If anyone has seen Mark Duplass in FX's "The League," they know how solid an improviser he is. Here he isn't lobbing jagged barbs at buddies like he does in "The League," but his improv is just as effective. There's a scene where Duplass and DeWitt are getting drunker as the night wears on and all you can do is laugh, it plays as a real and subtly hilarious conversation.

"Your Sister's Sister" features a story and situation you've seen a thousand times over in different variations, but how they handle it is key. There's an unexpected layer of refreshing optimism running throughout the movie. These characters are dealing with some weighty issues, but they aren't blubbering messes. They're dealing with their problems like real, honest-to-goodness people. Definitely worth your time, whenever it gets released.

Grade: B+