That Adams’ Delysia Lafosse comes across as so wonderfully artless and so charmingly guileless is a tremendous irony of Miss Pettigrew. Because there are, in fact, many things about Delysia that are less than, shall we say, unconstructed. She is, after all, a performer on the London stage in 1939: certain things are expected of her, certainly if she wishes to get ahead in her career. Certain things about her are not as they seem, and certain things she’s contemplating doing would not be true to her heart. Perhaps it’s that she’s never lying to herself: she knows what she’s doing. She is supremely confident in a way that is not overburdened with the weight of other people’s expectations about what she should do with herself. It’s a breezy kind of poise the likes of which is far more reminiscent of the screwball comedies of the 1930s and 40s that it is of any depiction of women in popular films that came after them. Modern movies seem to feel that women should pay for their independence by suffering and fretting over it, but there’s not a whiff of that depressing and unfair attitude here, which is part of why Miss Pettigrew is so delightfully refreshing.

Perhaps that’s due to the fact that this is based on a novel by Winifred Watson from the screwball era -- it was published in 1939 -- and that screenwriters David Magee (who wrote the lovely Finding Neverland) and Simon Beaufoy avoided any urge to “modernize” it. Not that everything is frothy and frilly here, for the Miss Pettigrew of the title is like something out of Dickens, a poor governess thrown out of her most recent job -- perhaps not unfairly, though, the film suggests -- who stumbles, almost literally, into a job as a “social secretary” for Delysia. Miss Pettigrew is played by the also-goddesslike Frances McDormand (Something's Gotta Give, City by the Sea), who refuses -- thank you, McDormand -- to make the at-first frumpy, seemingly stodgy Pettigrew into a caricature, as tempting as that may have been, and even as funny as that may have been. That same goes for Adams, too, actually: these two women actors take us far beyond the seeming cartoons their characters appear to be at the outset to a place at which their facades are shattered as the false fronts they have always been, outside this single day during which we are along for their ride.

And it is a ride, as Miss Pettigrew traipses along in Delysia’s wake over the course of 24 hours. It begins one morning, as Miss Pettigrew, who doesn’t realize at first that she has bluffed her way into a different kind of job than she was expecting, assists Delysia in gently but firmly removing the young man from her bed -- he would be the very handsome but slightly dim Phil (Tom Payne, who looks like Jude Law’s younger, brown-haired brother), an up-and-coming West End producer on the verge of handing her a juicy, high-profile role. Yes, Miss Pettigrew is far more risque than you might expect, and bracingly unembarrassed about it, as if, you know, sex and nudity were normal things and nothing to be ashamed of (huge kudos to director Bharat Nalluri [Tsunami: The Aftermath] there). And the story progresses throughout the day as Delysia prepares for the cocktail party that evening at which she expects to celebrate being handed that role.

Oh, yes, there is a handsome but poor piano player, played by Lee Pace (The Good Shepherd, Infamous) -- who, goodness, has Clive Owen’s smoldering eyes -- and a villain, played by Shirley Henderson (Doctor Who, Harry Potter and the Goblet of Fire) -- who once again proves she is one of the most underappreciated actresses working today, and that’s saying a lot, considering how underappreciated funny women are in general -- and even a possible love interest for Miss Pettigrew (who cleans up quite nicely) in Ciaran Hinds’ (There Will Be Blood, Margot at the Wedding) lingerie designer, Joe.

Yup, lingerie. I told you this was risque, but that’s not all it is, either. It’s funny, and yet poignant, too, like in how desperately hungry Miss Pettigrew keeps missing every chance for a bite to eat; and it’s sad, and yet somehow cheering and optimistic, too, like in how all the young people who don’t remember the last war welcome the beginning of the next (remember, it’s 1939, in London) -- it’s the first hint of the British pluck that will get them through it. But for all the roller coaster emotions -- I was in tears by the end, and they were tears of both happiness and sadness -- Miss Pettigrew does not hit a single wrong note. This could not be a more perfect movie.