The odd thing is, though, that Noel Coward didn’t quite write this version of Easy Virtue, either. The play this delightful and unexpectedly bittersweet new movie is based on was a melodrama, not a comedy, written when Coward was just a snip of a 23-year-old lad in 1924. (Alfred Hitchcock adapted it as a silent thriller in 1928, though how you eliminate Coward’s delectable wordcraft and still call it Coward is a mystery.) Director Stephan Elliott (The Adventures of Priscilla, Queen of the Desert) and his coscreenwriter, Sheridan Jobbins, are the ones who blended in the humor here. Oh, now, I’m sure there was a particular level of delicious sniping in Coward’s original work -- much of his dialogue was retained here -- and it’s almost certain that the unadulterated Coward, as sharp and forward-looking as he was, would still feel modern if presented to us unaltered.

But perhaps the inspired genius of this Easy Virtue is its intoxicating blend of the retro and the up-to-the-moment. I understand that some moviegoers find the contemporary brand of “humiliation comedies” -- movies like Meet the Parents -- amusing and even endearing because they come to feel sorry for and even infuriated on behalf of their put-upon protagonists. That same dynamic is at work here, when snappy American Larita (a luminous Jessica Biel: I Now Pronounce You Chuck and Larry, Next), arrives at the home of her new husband, British aristocrat John Whittaker (Ben Barnes: Stardust, The Chronicles of Narnia: Prince Caspian; look for him to be a major star), after their whirlwind romance, only to find that she is not at all welcome. Mortification and embarrassment are definitely in the offing for poor Larita... and without her ever having to get doused with the contents of a septic tank or be fooled into using a gob of semen as hair gel.

Nope, the withering will begin at the tongue of her new mother-in-law, Mrs. Whittaker (Kristin Scott Thomas [The Other Boleyn Girl, The Golden Compass], in perhaps the performance of her career). Some of her bile can be accounted for by Larita’s having had the bad taste to be born American; some of it will result from things outside Larita’s control that she will nevertheless take the blame for, accidents and misunderstandings and the like. But mostly, it’s because Larita had the audacity to take her only son from her.

Mrs. Whittaker is not the stereotypical evil mother-in-law, of course, as further events will confirm even for those who choose to see her that way early on. A plainly comedic cultural clash buoys the film early on, as the independent and experienced Larita tries to connect with John’s sisters, young and playfully morbid Hilda (Kimberely Nixon: Cranford) and older and dowdy Marion (Katherine Parkinson: How to Lose Friends and Alienate People), and finds a bit of surprising common ground with John’s distant father, Mr. Whittaker (Colin Firth [Mamma Mia!, The Last Legion], like Scott Thomas, giving one of his most intriguing performances ever). But the film gets darker in ways that Coward himself may not have been able to intend, for looming over everything here is our sure knowledge, with our historical hindsight, that the way of life that Mrs. Whittaker is trying to cling to for her family will absolutely come to an end, and soon. The specter of the devastation of World War I hangs over everything here -- particularly in the shape of Mr. Whittaker, a veteran, and one of the few men his age left alive in his community -- but though Coward may have seen the writing on the wall for the aristocratic way of life, we know for certain that the privations of the Great Depression and World War II are on the horizon, and the virtual taxing out of existence of the British aristocracy (or at least of their wealth) to pay for it all.

Which isn’t to suggest that there’s anything truly grim about Easy Virtue, just that the paradoxically cheery melancholy it finds in the end is well earned, and exactly right.