The story takes place on 14 February 1895. It is about two gentlemen pretending to be people other than themselves. Interwoven in their storylines are two romance-stricken ladies, each possessing an unusual allegiance to the manliness of the name Ernest. London man-about-town Jack Worthing, who hides behind the name Ernest, is an aristocrat from the country with uncertain lineage. His friend, Algernon Moncrieff, is of moderate means and has also created an imaginary character, Bunbury. Algernon's cousin, Gwendolen Fairfax, has caught the eye of Jack. Jack's ward in the country, Cecily Cardew, has caught the eye of Algernon. Lady Bracknell rules the roost with her heavy-handed social mores. The story begins in London. Jack and Algy are discussing life and love. Both reveal to each other their imaginary characters, Ernest and Bunbury. Jack reveals that he is in love with Algy's cousin, Gwendolen, and Algy reveals that he is in love with Jack's ward, Cecily. Both gentlemen begin to scheme the pursuit of their love. At tea that afternoon, Jack and Gwendolen secretly reveal their love for one another. Gwendolen makes it known that her “ideal has always been to love someone by the name of Ernest.” Jack fears she will find out his true identity. Lady Bracknell, in undulating purple silk Victorian attire, inquires as to Jack's pedigree. “Rise, sir, from that semi-recumbent posture. It is most indecorous.” Jack confesses that he does not know who his parents are because, as a baby, he was found in a handbag in a cloakroom at Victoria Station. “A handbag?” Lady Bracknell will not allow her daughter “—a girl brought up with the utmost care—to marry into a cloak-room, and form an alliance with a parcel.” At the manor house in the country, Cecily is daydreaming as her governess, Miss Prism, tries to teach her German. Uninvited, Algy arrives from London and assumes the role of Ernest. While Algy and Cecily are getting acquainted with the parlor, Jack arrives in black mourning clothes and informs Miss Prism that his brother, Ernest, is dead. When Algy and Cecily come out to see him, the sad news loses its believability as everyone now thinks Algy is Ernest. In pursuit of Jack, Gwendolen arrives from London and meets Cecily. They both discover that they are engaged to Ernest, not realizing one is Jack and one is Algy. When the men arrive in the garden, the confusion is cleared up. The ladies are put off that neither one is engaged to someone named Ernest. Lady Bracknell arrives, by train. As everyone gathers in the parlor, Lady Bracknell recognizes Miss Prism as her late sister's baby's governess from twenty-eight years before. “Prism! Where is that baby?” she bellows. Miss Prism confesses that she inadvertently left the baby in her handbag at Victoria Station. Jack realized they are talking about him. He retrieves the handbag from his private room and shows Miss Prism. She acknowledges that the bag is hers. Lady Bracknell then tells Jack that he is her late sister's son and the older brother to Algy. Unable to ascertain who his father was, Jack looks in an Army journal, as his father was a general, and realizes that his father's name was Ernest. Thus it becomes apparent that his real name is also Ernest - as Lady Bracknell says, being the eldest son, he must have been named after his father. The film ends with Jack saying, “I’ve now realized for the first time in my life the vital importance of being earnest.”
The film is largely faithful to Wilde's text, although it divides some of the acts into shorter scenes in different locations. Edith Evans's outraged delivery of the line "A handbag?" has become legendary. As actor Ian McKellen has written, it is a performance "so acclaimed and strongly remembered that it inhibits audiences and actors years later", providing a challenge for anyone taking on the role of Lady Bracknell. The film is noted for its acting, although the parts played by Redgrave and Denison called for actors ten years younger. Margaret Rutherford, who plays Miss Prism in this adaptation, played Lady Bracknell in the 1946 BBC production.
