Amid the patter, 'Miss Pettigrew' tips toward complex drama

It's fortunate that "Miss Pettigrew Lives for a Day" stars Frances McDormand and Amy Adams. Actors' showcases are only worthwhile if the actors are worth watching.

Based on the 1938 novel by Winifred Watson, it's a deluxe romance that most of the time plays like farce.

Guinevere Pettigrew (McDormand) is a middle-aged governess in 1939 London who has just been dismissed from yet another job. (She does not suffer fools gladly, or any other way.) Suddenly destitute, she bluffs her way into a job as "social secretary" to the flouncy, man-hungry American ingénue and singer Delysia Lafosse (Adams).

Delysia – sounds like "delicious" – is currently ensconced in the penthouse of her nightclub owner boyfriend (Mark Strong), one of three suitors she is juggling. The other two are Michael (Lee Pace), a pianist who is devoted to her, and Phil (Tom Payne), the spoiled 19-year-old impresario who, for the right amount of whoopee, may star Delysia in his new show on the West End.

Delysia is "entertaining" Phil when Miss Pettigrew walks in on them. What follows immediately is forced high spirits. If the movie had continued in this vein it might have ridden off the rails, but fortunately things calm down (somewhat). Director Bharat Nalluri and his screenwriters David Magee ("Finding Neverland") and Simon Beaufoy ("The Full Monty") like to pump up the proceedings with ultra-stylishness and high-speed patter. What they don't always recognize is that too much of a good thing is not always a good thing.

But it's also clear that the filmmakers, by opening on such a high note, are setting us up. We are led to believe that Delysia is simply a featherbrained gold digger, just as we are supposed to regard Miss Pettigrew as a loveless functionary. Both views, it turns out, are false, and the actresses are adept at letting us know this in small, measured increments. In its flighty way, "Miss Pettigrew Lives for A Day" is, of all things, a trenchant psychological drama.

Which is not to say it's a piece of edgy realism. Set entirely within the actions of a single day, it's framed as a fairy tale in which both women ultimately achieve their heart's desire. As musty as this sounds, and as musty as it sometimes is, the entire conceit is redeemed by the performances.

Adams emanates the same radiance she had in "Enchanted" – a more overt fairy tale. In that film, though, she was a blissful innocent. Here she's still an innocent at heart, but she's also far from virginal. Adams is capable of a full-scale emotional range even in a piece of fluff. (In some ways, the ideal role for her would be Holly Golightly in a remake of "Breakfast at Tiffany's"). It's to her credit that she handles the hard-bitten scenes in this film with the same aplomb as she does the earlier, ditzier material. Her presence is more enigmatic than you might expect: She challenges you to take her seriously.

McDormand doesn't overdo the mousiness in her early scenes, and this speaks to her integrity as a performer. Miss Pettigrew is the daughter of a vicar and her primness is taken for quite a ride by Delysia. But she needs a job and she also sees a chance to truly help the girl.

Miss Pettigrew is a classic example of someone who fixes other people's lives while her own is in disarray. When her Prince Charming appears, in the guise of a gallant clothing designer (Ciarán Hinds), she is lit up, softly, by his presence. It's a tribute to McDormand that we want to see Miss Pettigrew happy in the end. And because she is, so are we. Grade: B+

• Rated PG-13 for some partial nudity and innuendo.