Some actors “act,” emphasizing performance over empathy, while others, in some extraordinary way, simply become other people, disappearing completely into the widest variety of roles. Kelly Macdonald is one of the best of those, and in “Puzzle” she steps out and shows us what she can do on a bigger stage.

The Scottish performer has played a wide variety of parts since her 1996 debut as Ewan McGregor’s high school girlfriend in “Trainspotting,” including an astonishing, award-winning performance as a West Texas housewife in the Coen brothers’ “No Country For Old Men.”

But good as she is, Macdonald has never starred in a film until “Puzzle,” and her delicate but deeply felt performance, along with the work of top Indian actor and co-star Irrfan Khan and the rest of the cast, make this gentle, thoughtful yet pointed film the undeniable success it is.

The grace of Macdonald’s performance aside, a lot about “Puzzle” is unexpected, from having longtime producer Marc Turtletaub as its debuting director to its being based on “Rompe-­cabezas,” a 2010 film directed by Natalia Smirnoff.

Perhaps most unexpected is how completely involving the film’s scenario, written by Oren Moverman and Polly Mann, plays onscreen despite having a plot line about a woman’s unanticipated self-actualization that can sound schematic.

“Puzzle’s” opening sequence introduce Agnes (Macdonald) dutifully vacuuming the family living room. It’s a classic image of a housewife, which is the way Agnes, and everyone in her orbit, would describe her.

And Agnes is not just everyday cleaning, she is tidying the house and doing all the prep, including baking the cake and hanging the banner, for her own birthday party, a kind of self-sacrifice which turns out to be typical.

A devout Catholic, Agnes’ life revolves around the poles of family and church. Though we know the time is now because Agnes gets a smartphone as a birthday present, her life as we see it could be taking place 50 years in the past.

Husband Louie (Denman) is a burly guy who owns a garage in the community of Bridgeport, Conn. Older son Ziggy (Bubba Weiler) works there, not particularly happily, and entitled younger son Ronnie (Austin Abrams) has college in his sights.

Agnes definitely values her marriage, but there is also the sense that, as someone who fears change and gravitates toward predictability and stability, this is all that she knows.

Yet, if you look closely, there are signs of other aspects to her, a fascination with visual patterns, whether it be the stained glass windows in her local church or the pieces of a broken plate that have to be carefully glued together.

One of Agnes’ birthday presents, as it turns out, is a jigsaw puzzle, and on an impulse she takes the pieces out of the box and puts them together lickety-split.

Though Louie dismissively insists “only children play with puzzles,” the quiet pleasure Agnes gets from this achievement, like discovering a superpower she didn’t know she had, is written on her face.

The pleasure is so intense, in fact, that she overcomes a long-standing aversion to New York City and takes the train into town in search of more jigsaw puzzles to conquer.

While shopping at the puzzle store, a flier catches Agnes’ attention. “Champion,” it reads, “desperately seeking puzzle partner.” Agnes gets in touch, and “Puzzle” moves into a higher gear.

The champion turns out to be Robert (Khan, the star of “The Lunchbox” and numerous other films), a wealthy, sophisticated inventor who lives in a Manhattan townhouse and is unlike anyone Agnes has ever known.

Robert recognizes Agnes’ gift at once and enlists her to be his partner.

Agnes, for her part, is equal parts wariness about Robert and delighted at doing something she was born to do. She feels she has to keep this new pleasure from her family as well as fend off Robert’s curiosity about her personal life. What is surprising is how delicately this film threads the needle between the different aspects of her life and leaves us satisfied with its conclusion.

The triumph of “Puzzle” and its heroine is not so much, as someone says, “getting all the wrong pieces right,” but the realization that none of the pieces are wrong, they just may not be right for you.

“PUZZLE”

****

(R, 1:43)