A superb cast brings Oscar Wilde's classic comedy of manners to life in the third big-screen adaptation of this hilarious look at fun, games, and dubious ethics among the British upper crust. Algernon Moncrieff (Rupert Everett) is a slightly shady, but charming gentlemen from a wealthy family who has a bad habit of throwing his money away. Algernon has a close friend named Jack Worthing (Colin Firth), a self-made man who acts as a ward to his cousin, a beautiful young lady named Cecily (Reese Witherspoon). Algernon has created an alter ego to help him get out of tight spots brought on by his financial improprieties, and when he learns that Jack has created a false identity of his own -- Earnest, a brother living in London whose exploits have earned him no small amount of notoriety -- Algernon arrives for a weekend visit in the country posing as the mysterious Earnest. Having heard of Earnest's misadventures many times over the years, Cecily had developed something of an infatuation with the lovable rogue, and Algernon's impersonation of him works no small degree of magic on Cecily. Meanwhile, Algernon's cousin, Gwendolyn (Frances O'Connor), arrives for the weekend, and is startled to discover Jack is also there -- except that she knows him as bad-boy Earnest. So just who is in love with who? How will Lady Bracknell (Judi Dench) handle the matter of her daughter Gwendolyn's suitors? And what's the truth about Jack's mysterious heritage?
Summary from: http://www.fandango.com/theimportanceofbeingearnest_v261812/plotsummary