Lady Bracknell returns to the room, and Gwendolen tells her she is engaged to Jack. Lady Bracknell then interviews Jack to determine Jack’s eligibility as a possible son-in-law. Jack seems to be giving all the right answers, until Lady Bracknell inquires into his family background. Jack explains that he has no idea who his parents were, and that he was found, by the man who adopted him, in a handbag in the cloakroom at Victoria Station. Lady Bracknell is scandalized. She forbids him from marrying Gwendolen and leaves the house angrily.
Algernon enters, and Jack reviews the results of his interview with Lady Bracknell, explaining that as far as Gwendolen is concerned the two of them are engaged. Algernon asks mischievously whether Jack has told her the truth about being “Ernest in town, and Jack in the country,” and Jack scoffs at the idea. He says he plans to kill off Ernest by the end of the week by having him catch a severe chill in Paris. Algernon asks whether Jack has told Gwendolen about his ward, Cecily, and again Jack scoffs at the question. He claims Cecily and Gwendolen will surely become friends and “will be calling each other sister.”
Gwendolen reenters and asks to speak privately with Jack. She tells him how the story of his childhood has stirred her and declares her undying love, whatever happens. She asks Jack for his address in the country and Algernon listens in, jotting it down on his cuff. Jack exits with Gwendolen to show her to her carriage, and Lane comes in with some bills, which Algernon promptly tears up. He tells Lane he plans to go “Bunburying” the next day and asks him to lay out “all the Bunbury suits.” Jack returns, praising Gwendolen, and the curtain falls on Algernon laughing quietly and looking at his shirt cuff.