Jack Worthing has made up a good for nothing brother named Earnest in order to go up to town whenever he likes. While in town Jack takes on the identity of Earnest, and it is as his fictional brother that he meets and falls in love with Gwendolen. He proposes marriage to her but her mother is shocked to discover that Jack was adopted as a baby after being found in a handbag and refuses to let him marry her daughter unless he can find his real parents.
Jack returns to the country in an effort to find his biological parents but his friend Algernon shows up, telling people he is brother Earnest and starts courting Jack's ward Cecily. Things get more complicated when Gwendolen arrives and both she and Cecily claim to be engaged to Earnest. Both men have some explaining to do and must be quick on their feet if they want to keep the women they love.