There are probably no better hands to entrust virtue of any sort to than those of writer-director Stephan Elliott, the Australian filmmaker who brought such delightful flamboyance to the drag queens at the generous heart of “The Adventures of Priscilla, Queen of the Desert.” A ski accident pulled him out of the movie game for years until some clever producers tracked him down and got him to help adapt and then direct “Easy Virtue,” a Noel Coward comedy of manners. It’s great to have Mr. Elliott back.

The setting is the British countryside post-World War I, decades before Elliott’s drag queens invaded the outback, but the problems are the same: old conventions fighting off inevitable change.

In this case we have the Whittaker family, typical of the landed gentry of the ’20s and ’30s, which means trying to cover their uncomfortable new impoverished state with the occasional fox hunt, ladies’ teas and the nightly formal dinner, butler included.

Everything is fraying around the edges of this family. Headed by Kristin Scott Thomas, this tightly wound matriarch is betting the bank on son John’s return, having given up on her war-damaged husband, played by Colin Firth. There are the requisite unmarried daughters in the mix too.

John (Ben Barnes) sweeps back into this dangerous brew, all dashing carefree charm, with a big surprise for mummy. The boy has come back married to an American. If that weren’t crime enough, Larita, played by Jessica Biel, is dangerously glamorous, drives race cars, smokes cigarettes and, from the looks of it, enjoys spending money. She also is not one bit afraid of the formidable Mrs. Whittaker.

Biel’s looks alone make her ideal for the role. She has a very American fresh-scrubbed openness that is almost brash, and her long, lean body is made for the elegant slip satins that ever-so-gently skim those athletic surfaces. She’s a modern woman who says what she thinks, a characteristic that is particularly galling to her new mother-in-law.

It is a treat to watch Biel and Thomas go at it, though it’s hard to imagine anyone who could survive the quiver of acerbic barbs that Thomas delivers with unerring accuracy. She’s let herself go mousy and pinched for the part, and it’s as if that physical change unleashed a deliciously catty side that we’ve not seen up close.

Larita’s arrival sparks a different sort of fire in Firth’s Mr. Whittaker. He’s managed to survive the trenches, but he’s lost what little drive the war had left him to the disappointment he faced from his wife at home. He’s gone happily to seed, but nothing has been quite as pleasurable in years as watching his wife meeting her match.

Firth is an effortless actor, and he works that magic again here. But he is a generous one too, and everyone, especially Biel, benefits when he’s in the scene.

There is a clever sophistication to the story, which Elliott wrote with Sheridan Jobbins, but then it is rooted in a Coward play. At first it would seem that Larita is the woman of easy virtue, as the Whittakers keep discovering the skeletons in her closet. Mrs. Whittaker, and then John’s sisters too, become convinced that Larita’s seduced their gullible boy for his money, though there is none. And their shock at everything about this interloper is really barely masked delight.

Of course, it’s not Larita’s virtue that is in question at all. Throughout the film, it’s anyone’s game as to who will win in the end. What is a given is that everyone will be bruised along the way.