The third act opens in Lord Goring's house while he prepares to go out for the evening. There is a description of the room and of Phipps the butler who Wilde describes as the "dominance of form." In the stage notes, Phipps is referred to as the "ideal butler," and his main distinction is his impassivity. Lord Goring enters in very fine attire, and Wilde proclaims that he masters modern life as the first well-dressed philosopher. Goring speaks to Phipps, but the conversation is clearly very one-sided as Goring espouses about fashion, society, and his buttonhole through a series of epigrams. Throughout the conversation Phipps simply plays the yes man and demonstrates no discernible personality. Phipps hands him three letters delivered earlier in the day. One is from Lady Chiltern, who wrote, "I want you. I trust you. I am coming to you." The letter is not addressed to anyone, but it is signed "Gertrude".
Lord Caversham enters to the dismay of his son. He makes himself comfortable and makes it clear he wants to have a serious talk. He tells Lord Goring that he must be married, and since bachelors are no longer in fashion, he must do so at once. While Lord Caversham calls him heartless, Lord Goring resorts to trivial discussion of his buttonhole. They move into the smoking room, and Lord Goring comments on the state of sympathy in the modern world. His father takes his comment as a paradox and wonders aloud whether his son understands what he says. The conversation between the two men is quite lengthy and demonstrates the differences in age and perspective between them. Lord Caversham complains of a draught in the room, and Goring suggests they move to the smoking room. As Caversham goes into the smoking room, Lord Goring takes an aside to instruct Phipps that a lady is calling on him and to show her into the drawing room to wait for him. He tells Phipps that it is the matter of gravest importance and that no one else but this lady should be admitted. Lord Goring then attends to his father in the smoking room.
Harold the footman shows Mrs. Cheveley in. She asks for Lord Goring, and Phipps explains he is presently with Lord Caversham. He also tells her that Lord Goring has asked if she would be kind enough to wait in the drawing room, where he will come to her. Mrs. Cheveley is surprised that Lord Goring seems to expect her. Phipps explains that Goring told him if a lady were to call he should have her wait in the drawing room, and he opens the drawing room door for Mrs. Cheveley. Mrs. Cheveley makes a comment to herself about how expecting the unexpected shows a modern intellect, and then looks into the drawing room. She declares that it is a dreary bachelor's room and that she will have to alter all this.
Mrs. Cheveley begins wondering what woman Lord Goring is waiting for and looks forward to "catching" him. She rifles through Goring's papers and correspondence and after recognizing Lady Chiltern's handwriting on one of the letters, reads it. A "look of triumph" appears on her face. She almost steals the letter but Phipps appears in the room. He tells her the candles are lit in the drawing room and she follows him in. After Phipps retires, she sneaks back towards the writing desk in the other room, but hears voices from the smoking room growing louder an quickly retreats to the drawing room.
Lord Goring and Lord Caversham argue about marriage. Goring wants to choose the girl, time and place for himself. Caversham believes he would make a foolish decision. Goring escorts Lord Caversham to the door and somewhat helplessly returns with Sir Robert Chiltern. Chiltern says he is so glad to find Goring at home, but Goring replies that he is very busy and cannot see him. Chiltern tells him that his wife has discovered everything from Mrs. Cheveley and that Goring must talk with him. He buries his face in his hands. Upon questioning from Lord Goring Chiltern says he has heard back from Vienna and that nothing valuable was sent. He only learned that Mrs. Cheveley occupies a high position in society and that Baron Arnheim left a lot of his wealth to her. Robert keeps repeating that he doesn't know what to do and asks Goring if he can trust him, to which Goring replies in the affirmative. When Goring goes out to speak with Phipps he discovers that the lady he was expecting is waiting in the drawing room. Thinking that the lady is Lady Chiltern he decides that he will give her advice through the door with his conversation with Robert Chiltern.
Returning to Robert, Goring asks him if he loves his wife, and Robert replies that he loves her more than anything in the world. Goring then says that since Lady Chiltern loves him she will forgive. Goring tries to get Chiltern to leave but Chiltern says he must stay for five minutes to tell him what he is going to say in the House on this night about the Argentine Canal deal. There is a sound of a chair falling from the drawing room. Chiltern wants to know who has been listening to his secrets. Goring denies anyone is there, but Chiltern insists that someone must be in the drawing room. He demands to see for himself.
Chiltern rushes to the door and Goring finally admits that someone is inside who cannot be revealed. Chiltern goes in anyway and Goring is dismayed thinking Lady Chiltern has been discovered. Sir Robert returns looking angry and asks for an explanation. Goring, who does not yet know that Mrs. Cheveley is in the drawing room, says that the lady is stainless and guiltless of all offenses. Chiltern replies that she is a vile and infamous thing. Goring goes on trying to defend the woman he thinks is Lady Chiltern, while Sir Chiltern continues to throw insults and accusations at Mrs. Cheveley and also Lord Goring, calling him a false friend and an enemy.
Sir Robert leaves and Mrs. Cheveley reveals herself to an astonished Lord Goring. He recovers from his shock quickly and the two begin talking. Lord Goring correctly guesses she has come to give him Sir Robert's letter to Baron Arnheim. We learn that in their youth, Mrs. Cheveley seduced Lord Goring for financial gain. However, she claims her love for him is stronger than ever, and says she will hand over the letter if Lord Goring marries her. She explains that she wants to settle down in London, and that when she saw Goring at the party the previous night, she realized he was the only person she ever cared for. Lord Goring responds by claiming he would be a very bad husband and indicates he does not wish to marry. Mrs. Cheveley says she expected him to show self sacrifice by marrying her to save Sir Robert's career, but Lord Goring replies that he believes self-sacrifice should be outlawed because it is so demoralizing to those it benefits.
Mrs. Cheveley says nothing can demoralize Chiltern's character based upon his corruption, and Goring jumps to his defense saying it was not worthy of him and merely a mistake of youth. Mrs. Cheveley comments on how men stand up for each other, and Goring replies that women are always at war with each other. Mrs. Cheveley explains the only woman she is at war with is Lady Chiltern. Mrs. Cheveley readies to leave and wants to shake hands with Lord Goring but he refuses, saying there can be no forgiveness for what she did to the gentle Lady Chiltern. Mrs. Cheveley says she had not gone to Lady Chiltern with the purpose of revealing her husband's guilt, but had in fact visited with Lady Markby to ask about a brooch lost at the party. Lord Goring asks if it is a diamond snake brooch with a ruby, and Mrs. Cheveley confirms that it is. Goring has meanwhile pulled the brooch from his drawer. He tells her he found it and deftly puts it on her arm. Mrs. Cheveley is surprised, as she didn't know it could be used as a bracelet. Goring says it looks better on her than the last time he saw it, which was ten ago on Lady Berkshire to whom he gave it as a wedding present. Goring accuses Mrs. Cheveley of stealing the brooch, although at the time a servant was accused and disgraced. She denies it, and tries in vain to remove the bracelet. Goring explains that the spring clasp is impossible to find unless you are shown where it is. Mrs. Cheveley becomes panicked, scratching at her wrist. Lord Goring, who has gained all the power in this interaction threatens to have his servant fetch the police. Terrified, Mrs. Cheveley asks him not to, saying she will do anything for him. He demands Sir Robert's letter to Baron Arnheim, and after some stalling she gives it to him. Afterwards, she asks for a drink of water.
When Lord Goring's back is turned she steals Lady Chiltern's letter. She then tells Lord Goring she is going to render Sir Robert Chiltern a great service by showing him how he has been deceived in his marriage, and explains she will forward Lady Chiltern's apparent love letter to Sir Robert. Goring tells her to give it back, threatening force. He rushes toward her but she presses the servant bell and Phipps enters. Slyly, she tells Phipps that Goring rang him so he could show her out. She leaves with a look of triumph.
In the opening stage directions, Wilde describes Lord Goring as a master of modern life. In the next scene, Lord Goring tutors Phipps about fashion, falsehoods, and vulgarity with many of Wilde's epigrams that highlight Goring's selfish view of the world. Goring describes vulgarity as a problem of "others", and refined behavior as characteristic of the individual. Ironically, Goring is clearly extremely self-involved, but also is the only character working to save his friends' marriage and protect their images. Although Lord Goring represents generosity and is a good friend throughout the play, he still remains a very egotistical character. His attention to a buttonhole is so trivial that one might consider it an allegory for other characters' obsession with other materials, such as social status or wealth. Throughout this opening scene, Phipps is a comedic tool with an impassive demeanor, responding to all of Goring's statements without emotion and with simple agreement and affirmation.
Lord Goring receives a letter from Lady Chiltern, and resolves to make her stand by her husband, Sir Robert Chiltern. In his view, every woman must stand by her husband, and he laments the growth of moral sense in women, which he believes is responsible for making the institution of marriage hopeless and one-sided. The validity of this claim is questionable at best, but reminds the reader that Wilde wants to emphasize the foolishness of the Chilterns for trying to construct the perfect marriage.
Lord Goring and his father Lord Caversham have a very lengthy discussion that presents the opposition of their world views. Lord Caversham, an aged and respected man, represents conservative London society and the morals of the Victorian era, which encourage a focus on family and public and private success. However, his son is a dandy who lives beyond the restrictions conservative society would impose on him, is extremely narcissistic, and places pleasure, beauty and idleness at the forefront of his life. The two men find it very difficult to see eye to eye. In fact, throughout their conversation, Lord Goring's wit and irony are hard for Lord Caversham to follow and result in his general confusion. Lord Caversham argues that his son should marry for practical reasons such as property and name, while Goring plans to marry only for love. His father sees an immediate need to take action, but Goring claims he is still a young man and need not think so seriously about such things. In reality, Goring is in his mid thirties, and as a dandy is living his life with a false sense of youth. In addition, Lord Caversham urges Lord Goring to enter some kind of professional work and perhaps follow the example of Sir Robert Chiltern who is such a noble servant of the government. The irony of this suggestion is quite clear.
In his conversation with Sir Robert Chiltern, Lord Goring focuses on two aspects of the situation: love and forgiveness. The mistaken identity of the woman behind the door is highly ironic, as the evil Mrs. Cheveley stands in the place of the idealistic and good Lady Chiltern. Sir Robert's discovery of Mrs. Cheveley furthers the plot and adds yet another complication to the problems Lord Goring must solve.
When Mrs. Cheveley and Lord Goring are left alone together, the two are clearly equals. They mirror each other in the quality of dress and presentation, and also in their selfish perspectives. However, Lord Goring, who demonstrates an eagerness to help his friends and right wrongs, proves superior. First, Lord Goring offers Mrs. Cheveley money for Sir Robert's letter, but she scoffs at the proposal. Here, again, money has no real power in social context. Instead of accepting money, Mrs. Cheveley wants to marry Lord Goring in exchange for the letter, claiming he is the only man she ever really loved. In Lord Goring's eyes, Mrs. Cheveley has desecrated the idea of love through this proposal and through trying to kill Lady Chiltern's love for her husband, an act he can never forgive. As such, Lord Goring refuses her offer and therefore removes her bargaining power.
The idea of forgiveness has some emotional pull, even on a character like Mrs. Cheveley, for she feels the need to explain that she went to the Chiltern house to find her lost brooch rather than to reveal Sir Robert's moral faults. As a result, Lord Goring discovers that she stole this brooch from Lady Berkshire, and he suddenly holds all the power in their interaction. The brooch/bracelet is a pivotal object in the play. The diamond snake shape alludes to the evil character of Mrs. Cheveley who is suddenly trapped by it. When placed on her wrist, Mrs. Cheveley cannot escape and her true character is revealed. Clawing at the bracelet, threatened with legal action, and suddenly without any bargaining power, she becomes so angry that she cannot speak, and the monstrous being underneath the guise of her makeup and dress reveals itself. Again, a mask is pulled away and a true identity discovered.
The two letters are also clearly very important objects. Lord Goring succeeds in capturing the letter from Sir Robert to Baron Arnheim, but Mrs. Cheveley succeeds in stealing Lady Chiltern's apparent love letter to Lord Goring. In this act, both letters and the brooch all pass through both Lord Goring's and Mrs. Cheveley's hands. Clearly, the interaction between these two pivotal characters will lead to the play's resolution. At the conclusion of this act, the reader is relieved that Sir Robert's public image is no longer threatened, but wonders at the power and influence of Lady Chiltern's letter to Lord Goring, which has suddenly fallen into the wrong hands.
At the end of the act the stage directions note that Mrs. Cheveley has a look of evil triumph, the second time a look of triumph has graced her face this act (the first when she entered the scene from the drawing room to Lord Goring's surprise). The idea of triumph was introduced at the end of Act I with the tapestry, "Triumph of Love." Mrs. Cheveley's triumph at the end of this act leaves the reader questioning whether in the end, love or evil will win. Currently, it seems evil has the upper hand.