Lady Wishfort returns with the letter in her hand and she invites the dancers to perform. The dance doesn’t serve any dramatic purpose and seems to be just awkwardly tacked in. Maybe Congreve just had some dancers at his disposal, like the singer a few scenes earlier. After the dance Lady Wishfort says she is going to read the letter in Sir Rowland’s presence, to show him that she has nothing to hide. Foible recognizes Mrs Marwood’s hand and whispers frantically to Waitwell to prevent Lady Wishfort from reading it. Waitwell pretends to be very jealous about the letter and threatens to kill its author, but Lady Wishfort says reading the letter in his presence should set mind at ease. The letter, sent anonymously by Marwood, says that “Sir Rowland” is an impostor. Lady Wishfort gets very upset and quick-thinking Foible tells Waitwell to say that it’s from his nephew. So “Sir Rowland” swears he recognizes his nephew’s hand and says he is going to bring the black box with all the documents confirming his status. Foible confirms his version, saysing she saw Mirabell talking with Millamant today and it must have been then when he left the letter. Lady Wishfort seems to believe them, but says seeing the contents of “Sir Rowland’s” black box will set her mind at ease. She begs him not to fight his nephew and let himself be hanged as a result, and she promises to sign the marriage contract when he returns.
Enter Waitwell as “Sir Rowland”, to whom Lady Wishfort apologizes profusely. Sir Rowland tells her it’s OK, it’s just that he’s unhappy when she is for too long away from him. Lady Wishfort proposes they should put off their wedding for a day or two “for decency of marriage”, but Sir Rowland has none of it. “For decency of funeral, madam”, he answers”, explaining his nephew is sure to poison him when he hears about the impending marriage and he wants very much to starve him by marrying (presumably blocking in this way his inheritance). Lady Wishfort pricks up her ears, being very interested in hurting Mirabell as well for his perfidious behaviour (i.e. pretended wooing). “Sir Rowland” pretends he is jealous about Mirabell as a rival and wants to kill him, but Lady Wishfort says, better starve him, not that I have any personal interest in that. She talks a lot about how she is absolutely not motivated in her urge to marry by any sort of carnal desire and “Sir Rowland” pretends to believe her. Enter Foible to tell Lady Wishfort that the dancers have arrived and there is also a messenger with a poste-restante letter to her. When she leaves, Waitwell says to his real wife that he needs a drink and that this pretended courtship is really a very arduous business.
Enter Sir Wilfull with Lady Wishfort. Sir Wilfull is drunk, breaks out into a song and proposes to Millamant, while Lady Wishfort chides him all the while. Millamant can’t stand him and leaves. Exasperated Lady Wishfort wishes he travelled as far as Turkey or the land of the Tartars, but Sir Wilfull says they don’t drink alcohol there and sings a midly offensive ditty about it. Enter Foible and whispers something to Lady Wishfort, apparently telling her that “Sir Rowland” is getting impatient. Lady Wishfort asks Witwoud to take care of his brother. Witwoud doesn’t have an idea what to do with him and proposes going to see a cockfighting match. Sir Wilfull answers with some lame sexual jokes (“with a wench?”) but agrees to follow his brother Anthony, making some slightly better jokes about how his brother Tony is St Anthony and he is his pig, because St Anthony the Great was usually portrayed with a pig. Sir Wilfull exhibits, I think, a much better knowledge of Catholic iconography than you could assume with a (presumably) Protestant Englishman who’s never been abroad. They leave.
Enter Mrs Fainall. Millamant finally admits she is going to accept Mirabell’s proposal, doing it with a lot of hedging – “I’ll endure you” – but finally is coaxed by Mrs Fainall and Mirabell to admit her love. Fainall tells Mirabell to leave because Lady Wishfort is coming and she is sure to get fits if she sees him, which in turn would impede “Sir Rowland’s” courtship of her, so there is no time for long goodbyes. When Mirabell leaves, Mrs Fainall tells Millamant that Sir Wilfull is drunk and her mother had to leave Sir Rowland to intervene between him and Petulant, to which Millamant answers that she is going to be very unhappy if Mirabell doesn’t make a good husband, because she loves him violently. That must be true, says Fainall, because you don’t hear what I’m saying. Enter Witwoud, telling Fainall that Petulant and Sir Wilfull are very angry with each other, but nobody knows why, because there is a lot of sputtering on both sides and no dispute. He finds it very funny. Enter Petulant drunk. He proposes to Millamant and banters with Witwoud, whom as usual he offends, calling him and his brother “a Gemini of asses” and various other inventive insults, and Witwoud as usual doesn’t take offense, but finds it very funny. How did you all get so drunk, asks Mrs Fainall. It was all your husband’s plan, says Witwoud, but he sneaked off.
Enters Mirabell, ending the line quoted by Millamant, thus proving that unlike Sir Wilfull he is not a boor. He asks Millamant whether she will finally accept his proposal. Millamant says, but only very conditionally. She sets down a lot of provisos, which boil down to the same thing: she still wants to be independent after marriage and pursued like before. So no cuddling and affectionate terms in public, her husband always has to knock on the door of whatever room she is in, she is to lie in bed in the morning as long as she pleases, come to dinner when she wants or to have it in her own room, and she is always going to be the mistress of her own tea table, to which her husband is going to be allowed only if she lets him too. Also no censorship of her letters, no forcing her to spend time with people she doesn’t like only because they are her husband’s family or friends. Mirabell says, very well, but then I have my stipulations, too. No masks by day (of the kind which Marwood wore in Act 2) or heavy cosmetics by night, no mixing with the court ladies, no clothing pedlars at home. You may have friends in general, but don’t pick one special female friend. When you are pregnant (Millamant shudders at the thought), no strait-lacing, because I don’t want to have crooked children. No strong drinks at your tea table with which you can drink toasts to other men, but I’ll allow “dormitives” like cowslip wine or poppy water. (I had no idea that was what cowslip wine was supposed to be.). Millamant says she has no intention of toasting men anyway. So, are we good, then? asks Millamant. Very opportunely, Mrs Fainall is just coming to be the witness.
Millamant still doesn’t notice Sir Wilfull, walking around the room pensively and reciting love poetry to herself (this must have been a very big room). She keeps on reciting poetry, saying with admiration “natural, easy Suckling!”. Sir Wilfull, being a boor, thinks she calls him a suckling and protests he is of age. Millamant says with disgust “Ah rustic, ruder than Gothic”. How shocked she is going to be when in a few decades her grandchildren will go crazy for Gothic. Sir Wilfull invites Millamant for a walk, but she says walks are a countryside pastime and she hates the country. Well, I guess some people prefer the town, says Sir Wilfull. I hate the town, too, answers Millamant, to which Sir Wilfull doesn’t really have a good answer. He hints at the possible proposal he might make to her later, but she asks him to leave her alone. With pleasure, but this door is locked, says Sir Wilfull. Millamant helpfully points to him the other, unlocked one, and he leaves.
Act IV begins after dinner which ended Act III, with Lady Wishfort all in a flurry to receive Sir Rowland. She told Foible to arrange all the servants in their best liveries in two rows along the corridor and to bring the coachman and the postillion in to make up the necessary number – but she had to spray some perfume on them first, to mask the odor of the stable. Lady Wishfort finally decides to receive Sir Rowland lolling on her couch, then startle when he comes, get up and come to greet him in sweet disarray. She also tells Foible to bring Millamant and she is going to call Sir Wilfull so that he can propose to her. Even in the era of arranged marriages this seems a bit fast. She hears the coach of Sir Rowland and leaves, telling Foible to come to her soon, so that she is not left with him alone for too long. Millamant and Mrs Fainall enter. Foible tells her that Mirabell has been waiting to see her for half an hour – shall she let him in? Don’t let him in, or let him in, I don’t know myself, says Millamant, who’s in a melancholy mood and quotes lines from various poems (by John Suckling and Edmund Waller) about what a misfortune is for a woman to love and put herself in power of a man. She finally tells Foible to let Millamant in and asks Mrs Fainall to entertain Sir Wilfull, as being married she has more experience to deal with fools. Oh no, I have my own business to take care of, says Mrs Fainall. Sir Wilfull enters and he is quite bashful. In the previous act Fainall said he was going to remove him from the competition for Millamant’s hand by making him drunk and thus disgusting to Millamant. But Sir Wilfull apparently hasn’t had enough yet, he says they don’t know each other well enough and he’s keen on going back to the dining room. Mrs Fainall eggs him on and then mischievously leaves the room and locks the door, even though Sir Wilfull rattles it and asks her to open.