Nigel, the Earl of Marshwood (Edward Atterton), romances the beautiful Hollywood star Miranda Frayle (Jeanne Tripplehorn), blissfully unaware of the consternation their impending marriage is causing both his mother, Felicity (Julie Andrews), the Countess of Marshwood, and Don Lucas (William Baldwin), one of Hollywood's most attractive by highly-strung stars and Miranda's former love—both on screen and off.

On the set of his latest picture in Hollywood, Don hits the Jack Daniels, whilst Felicity, presiding with her usual dignity and grace over Marshwood, decides to put a smile on her stiff upper lip and to accept Miranda—the Hollywood floozy—as her prospective, although class-wise totally inappropriate, daughter-in-law and future Countess. Felicity is further shocked when her long-standing personal maid, Moxie (Sophie Thompson), now tearfully threatens to leave, finally confessing that Miranda Frayle, the future Countess of Marshwood, is none other than her long lost sister whom she has not seen for twenty years.  And so, with the help of her nephew Peter (Colin Firth) and Crestwell (Stephen Fry), Marshwood's urbane butler, Felicity sets about creating an ingenious change of image for Moxie, upgrading her to house guest, making her socially acceptable at Marshwood for her sister's imminent arrival.

Nigel and Miranda arrive at Marshwood to be cordially greeted by Felicity and Peter, and the ranks of the downstairs household who are in a state of star-struck excitement.  Miranda does not recognize her sister, and Felicity secretly tells an astonished Nigel that Moxie has inherited a small fortune—of course Felicity never reveals to him that Moxie is Miranda's sister.

Adding fuel to the fire, Don has pursued Miranda to England and arrives at Marshwood drunk, distressed and desperate to reclaim his gal who is both flattered and mortified to see him.  But his visit is a source of great delight to Felicity who—catching them in a stolen kiss—realizes that Don fits perfectly into her own little plan.

Meanwhile, the presence of two of Hollywood's most glamorous stars has caused something of a riot at the gates of this stately English home as teenage fans clamor to catch a glimpse of them.

During dinner, Miranda blithely and foolishly concocts horrible stories about their impoverished childhood and their alcoholic mothering an attempt to dramatize what was, in fact, a rather conventional and boring early life.  Moxie, unable to control her rising anger over Miranda's outrageous lies, finally blurts out who she really is and exposes her ridiculous charade to a mortified Nigel.

The hopelessly snobbish Nigel, now realizing that he cannot possibly marry his mother's maid's sister—movie star or  not—leaves Miranda in the lurch and Don to the rescue. Marshwood is consumed by chaos and the Relative Values of a post-war class system are hilariously exposed.

“I was instantly attracted to the role because of Noel Coward’s wonderful writing. You simply cannot get better dialogue; his lines are airy, witty and beautifully constructed.  I had never performed Coward before so it was slightly like going into uncharted water which was exciting.”

“Peter basically spends his time hanging around the place. He’s a harmless mischief-maker who enjoys the crisis that’s unfolding and he treats it all as a bit of a game. I haven’t modelled my character upon Noel Coward because it is very important to appropriate a role and make it your own. After all, the delivery of a line now is certainly not going to be the same as it was forty years ago.”