Jessica Biel and Ben Barnes star in Stephan Elliott's film of the Noel Coward play Easy Virtue. (Alliance Films)

There are few things more embarrassing than an old person – or an old play – trying to be hip. Stephan Elliott's well-meant but ill-conceived adaptation of Easy Virtue strives to give Noël Coward's Jazz Age comedy a modern makeover. And like, say, your granddad doing the stanky leg, the effort only looks awkward and foolish.

Jessica Biel looks smashing in those vintage cloche hats, but she hasn't got the kind of forceful personality to turn a household topsy-turvy.

Writer-director Elliott and his co-scenarist, Sheridan Jobbins, retain much of Coward's cut-glass wit, but then cheapen it with coarse gags like a chihuahua-killing scene swiped from The Sopranos. Marius De Vries's soundtrack treats us to period tunes by Coward and Cole Porter, but also to awful, jazzed-up arrangements of Rose Royce's Car Wash and Tom Jones's Sex Bomb. The cast includes such top-drawer actors as Kristin Scott Thomas and Colin Firth, but the lead is played by Jessica Biel, better known for dating Justin Timberlake than for her acting chops.

Australian filmmaker Elliott is best known for the 1990's drag-queen comedy The Adventures of Priscilla, Queen of the Desert, which may explain his crass, kitschy impulses. It doesn't explain why he can't seem to figure out what kind of movie he's making.

After hearing Biel's torchy cover of Coward's Mad About the Boy — featured under the opening titles — I had high hopes. If the picture were anything like her version of that song, it would be fresh yet faithful to the spirit of the original. Instead, the film is an atonal mess. Elliott can't seem to decide if he's making a comedy of manners or a serious family drama. One minute, a glum Colin Firth is brooding over the Lost Generation, the next, a bubbly Ben Barnes is breaking into song. (Every time he does, you think the movie is going to turn into a musical.)

Coward's 1925 play is a critique of social hypocrisy, in which a brash woman shakes up a smug British family by marrying their only son. Here, Biel plays the woman of easy virtue: Larita, a free-spirited American flapper and race-car driver, who falls madly for boyish John Whittaker (Barnes) while competing in the Monte Carlo Grand Prix. John brings Larita home to the family manor in England, where a clash of cultures and morals ensues.

Kristin Scott Thomas plays Mrs. Whittaker in Easy Virtue. (Alliance Films)

Larita's main adversary is Mrs. Whittaker (Scott Thomas), a tweedy specimen of upper-class repression who quickly brands her new daughter-in-law a gold-digger and a floozy. Larita, for her part, proves averse to the family's cherished English traditions: she thinks fox hunting is barbaric, is allergic to flowers and refuses to take exercise in the chill morning air ("Shackleton wouldn't let a dog out today," she declares with a shiver). Worse, she passes on "pornography" (a copy of Lady Chatterley's Lover) to John's older sister, Marion (Katherine Parkinson), and inadvertently encourages impressionable younger sister Hilda (Kimberley Nixon) to perform the can-can sans knickers.

Larita's only ally among her in-laws is John's father (Firth), a bitterly disillusioned First World War vet who knocks about the manor, unshaven, chain-smoking and, in Larita's words, "quietly sardonic." Like Larita, he knows the British attitude of moral superiority is a hollow sham.

Larita wants to escape to London, but callow John is reluctant to leave the nest and their fledgling marriage starts to founder. Things come to a head when Phillip Hurst (Christian Brassington), son of the local peer and the object of Hilda's affections, ends up falling for Larita instead. Hilda, outraged, unearths a scandal in Larita's American past and spreads the news.

Like Hay Fever, Coward's previous and more famous play, Easy Virtue takes great delight in dissecting a dysfunctional upper-crust family. Although Mrs. Whittaker struggles to keep up appearances and "brazen things out," she and her brood are a sorry lot. Marion is still obsessed with a fiancé who wisely ran away; Hilda gets her vicarious thrills collecting clippings of crimes and scandals. Mrs. Whittaker herself is unusually cozy with the widowed Lord Hurst (Pip Torrens) – not surprising, considering Mr. Whittaker has become more like a cynical outsider than a member of his own family. Larita's arrival exposes the shallowness and fraud running through the Whittaker clan like dry rot.

When Elliott sticks to this family portrait and doesn't try to juice things up with his faux-Roaring Twenties joie de vivre, the film finds its best moments. Scott Thomas, looking like Virginia Woolf, is gloriously good as Mrs. Whittaker: as brittle as a Ming vase, she snaps off the Coward lines with relish, like she was biting into celery. But her careworn face betrays the Herculean strain of maintaining a proper façade while the family fortunes slide. (It turns out there isn't much gold for Larita to dig.)

Colin Firth and Jessica Biel dance in a scene from Easy Virtue. (Alliance Films)

Parkinson and Nixon as the giggly sisters are precisely the kind of fatuous girls Coward loved to mock. Barnes is appropriately foolish and innocent as John – even if his nickname, Panda, makes little sense; he's more like a frisky puppy dog. Firth, recycling his moody Mr. Darcy persona, is sadly disappointing. As the man who sees through pretensions, his performance is, ironically, pretentious.

As Larita, a platinum-blond Biel looks smashing in those vintage cloche hats and could have taken smoking lessons from Gertrude Lawrence herself. Only she hasn't got the kind of forceful personality to turn a household topsy-turvy. Well-scrubbed and flashing a toothpaste smile, she's not the sultry sex bomb that blows up straitlaced society so much as a cheerleader dropped in the middle of a garden party.

Watching this flawed film, I felt increasingly frustrated because of the good things it has going for it: Scott Thomas's performance, Martin Kenzie's clever cinematography (the man is a master at shooting reflective surfaces), John Beard's loving period design. You imagine what the movie could have been in more skillful hands than Elliott's.

Easy Virtue was co-produced by the revivified Ealing Studios, which also did the 2002 remake of The Importance of Being Earnest. That picture likewise squandered a great cast (including Firth) in an overzealous attempt to sex up Oscar Wilde. I'm not sure why people who choose to film classic plays often go to such strenuous efforts to make them look trendy. Leave a play like Easy Virtue to its own devices, and you'll discover that Noël Coward needs no help being cool.

Easy Virtue opens in Toronto on May 29, in Montreal and Vancouver on June 5 and in Calgary, Edmonton, Ottawa and Victoria on June 12.

Martin Morrow writes about the arts for CBCNews.ca.