It is midnight when Higgins, Pickering, and Eliza enter the Wimpole Street laboratory, all resplendent in evening dress. The two men are talking with some animation, while Eliza is “brooding and silent.” Higgins and Pickering discuss how tired they are and how glad they are that the experiment is over. It has been a triumphant success for Higgins and, although Pickering gives Eliza some credit for the way in which she carried off the imposture, Higgins does not seem to register that she played any role at all. Pickering confesses to having enjoyed some of the day’s social events, but Higgins is relentlessly vehement about his boredom. He inveighs against the stupidity of society people, who spend all their time obsessing over trivial class distinctions yet do not have the wit to spot the impostor in their midst. He concludes that “the silly people don’t know their own silly business.”

Having decided to go to bed, Higgins starts hunting for his slippers. Eliza, who has been ominously quiet, though the stage directions describe her mounting fury, finds the slippers and throws them at him, displaying her anger at the way he is ignoring her after she won his bet for him. Higgins expresses astonishment when she tells him the reason for her resentment. He is entirely unsympathetic and arrogantly responds, “YOU won my bet! You! Presumptuous insect! I won it.”

Higgins has mentioned before (in act 3 particularly) that Eliza is a particularly apt and skilful pupil with a remarkable gift for mimicry, but he has never given her credit for what he regards as his triumph in the experiment. Eliza knows this, and it brings her anger to boiling point by this stage in the play. When she and Higgins begin to argue, however, it transpires that this lack of appreciation was only the trigger for her emotion. She has other, deeper concerns—the first of which is her future, which Higgins has continually dismissed as a matter beneath his concern. What is to become of her now that the experiment is over? What can she do now that she is a poor girl with the accent and manners of an upper-class lady? Higgins is still quite uninterested in the subject, expressing that she is now free and can do whatever she likes, as he can. He expects her to share his relief that the experiment is over. When Eliza persists, he makes some suggestions in a vague and desultory manner. He says she might marry, patronizingly telling her that she should not find it too difficult to acquire a husband, since she is “not bad-looking” and since most men might find her quite an attractive companion.

Higgins’s obvious boredom and condescension further enrage Eliza. She responds that even when she was a poor flower girl on Tottenham Court Road, she only sold flowers, not herself, adding, “Now you’ve made a lady of me I’m not fit to sell anything else.” Higgins clearly regards this as melodramatic, remarking that she doesn’t have to marry anyone she doesn’t like. He then suggests that Eliza stick to her original plan of working in a florist’s shop. Colonel Pickering, who has plenty of money, could probably “set [her] up in one.” He points out that six months ago, it was the summit of Eliza’s ambition to have a flower shop of her own. Now she seems to have grander, though ill-defined, goals which only appear to be making her fractious and unhappy.

Eliza’s manners to Higgins become cold and formal. She asks if her clothes belong to her or to Colonel Pickering, since she would not want to be accused of stealing them. She then asks Higgins to take charge of the jewels she is wearing for the same reason. Higgins is hurt and outraged by these words, as Eliza intended. He roughly takes possession of the jewels, and when Eliza hands him a ring he bought for her earlier, he violently hurls it into the fireplace. Eliza thinks, or pretends to think, that he intends to strike her. She shields her face and cries out, “Don’t you hit me.” This infuriates Higgins more than anything else she has said. He tells her that she has wounded him “to the heart” by suggesting that he is capable of such an action.

Eliza retorts that she is glad to have hurt him, as she has now “got a little of her own back.” Higgins regrets having lost his temper with her and moodily goes off to bed, finally observing that he has wasted his “hard-earned knowledge and the treasure of [his] regard and intimacy on a heartless guttersnipe.” Eliza smiles for the first time since the beginning of the scene. She is initially triumphant, but, after Higgins has left, she kneels down to look for the ring he threw away. When she finds it, she does not know what to do and eventually flings it away herself, then goes upstairs “in a tearing rage.”