George Bernard Shaw’s prefaces are usually long, complex works, often printed in a separate volume alongside the plays. The preface to Pygmalion is brief by Shavian standards, though Shaw begins by writing, “[this play] needs, not a preface, but a sequel, which I have supplied in its due place.” The preface deals mainly with phonetics and suggests various models for Henry Higgins, particularly the phonetician and grammarian Henry Sweet.

The first act begins at 11:15 p.m. on a rainy summer’s night in Covent Garden. Freddy Eynsford Hill is attempting to hail a cab when he bumps into flower seller Eliza Doolittle, spilling the contents of her basket on the street. As she remonstrates with him, a bystander points out that a man with a notebook is writing down everything they say. A crowd begins to assemble, and there is a general assumption that the notetaker is a police agent. However, he soon distracts them by telling all who address him what part of London they come from. When challenged to perform the same feat with a gentleman who is standing nearby, he promptly identifies the man’s hometown, school, university, and most recent residence with the words “Cheltenham, Harrow, Cambridge, and India.”

The gentleman is impressed by this accuracy and identifies himself as Colonel Pickering. The notetaker is Professor Henry Higgins. Both have published books on phonetics and are familiar with the other’s work. Higgins reveals that he makes his living by teaching rich people with low social origins to speak upper-class English, boasting that he could even teach Eliza, “with her kerbstone English,” to speak so perfectly that in three months, people would mistake her for a duchess. Higgins and Pickering then decide to have dinner together and leave. Eliza tries to sell a flower to Pickering as they go, saying that she has no money for her lodging. Higgins rebukes her for lying but then, hearing a church clock strike, impulsively throws a handful of money into her basket. This is far more money than Eliza was expecting to make from selling her flowers. Elated, she returns home in a taxi.

The second act opens the next day at eleven o’clock in the morning in Higgins’s laboratory in Wimpole Street. Higgins has been giving Pickering a tour when Mrs. Pearce, his housekeeper, announces that he has a visitor, who turns out to be Eliza. Higgins tries to send her away, but Eliza announces that she has come for lessons in English. Pickering reminds Higgins of his boast that he could pass Eliza off as a duchess after teaching her for three months, betting him the costs of the experiment that he will not be able to do it.

Higgins accepts the wager and instructs Mrs. Pearce to wash Eliza, burn her clothes, and order some more. While Eliza is bathing, her father, Alfred Doolittle, arrives, announcing that he has come to take Eliza away. Higgins correctly assumes that he would rather have money and gives him five pounds, assuring both Doolittle and Pickering that his intentions are strictly honorable and his only interest in Eliza lies in the phonetic experiment he is to conduct. As Doolittle leaves, Eliza reenters, freshly bathed and dressed in a kimono. Doolittle at first fails to recognize her. When he has left, Eliza remarks that she hopes he will not be back.

The third act begins on the “at home” day of Mrs. Higgins, Henry Higgins’s mother, between four and five o’clock, when she is expecting guests. She is not, however, expecting her son, who is unwelcome on these days, as he invariably behaves badly. However, Higgins enters and announces that he wants his mother to participate in an experiment. He has invited Eliza and intends to see how the guests react to her and whether they notice that she is not a member of their own social class.

As Higgins is explaining this, his mother’s guests arrive. Mrs. Eynsford Hill, her daughter, Clara, Colonel Pickering, Freddy Eynsford Hill, and finally Eliza enter the drawing room. Eliza is dressed exquisitely and looks beautiful, but she gives herself away almost as soon as she opens her mouth. She embarks on a long and highly inappropriate story about the death of her aunt, then goes on to discuss her father’s drunkenness. When she is about to leave and Freddy suggests walking across the park, she creates a sensation by announcing, “Walk! Not bloody likely. I am going in a taxi.”

After the Eynsford Hills have left, Mrs. Higgins tells her son that his experiment has been a complete failure. No one in upper-class society would ever mistake Eliza for one of their own. Moreover, she agrees with Mrs. Pearce that Eliza will never learn good manners while living with Higgins, since he behaves so atrociously himself. Both Higgins and Pickering exasperate Mrs. Higgins by their refusal to take seriously her questions about Eliza’s position in Higgins’s house as well as her future life.

The act ends with a separate short scene in which Higgins and Pickering take Eliza to a grand reception at an embassy. A former pupil of Higgins’s, named Nepommuck, who specializes in detecting impostors, declares that Eliza speaks English too perfectly to be an English aristocrat. He concludes that she is a Hungarian princess and rejects Higgins’s suggestion that she might be a girl from the English lower classes. Eliza is afraid that she has lost Higgins’s bet for him, but he tells her that she has won it ten times over.

The fourth act takes place at midnight in Higgins’s laboratory. Higgins, Pickering, and Eliza all enter, wearing evening dress. Higgins has won his bet, but he is now bored by the whole matter and wants to go to bed. When he starts searching for his slippers, Eliza throws them at him in a rage, showing her anger at his neglect and his refusal to acknowledge her role in the success of the experiment. She is also upset because her future is so uncertain now that the experiment is over. Higgins suggests, without much interest, that she might marry, or that Pickering could “set [her] up” in a florist’s shop. His obvious lack of concern further enrages Eliza, and she asks Higgins, with cold formality, to look after the jewels she is wearing, since she would not want to be accused of stealing them. Her attitude infuriates Higgins, and he storms off to bed, complaining that he has wasted his knowledge and regard “on a heartless guttersnipe.”

The fifth act begins with Mrs. Higgins in her drawing room. Higgins and Pickering enter in consternation, saying that Eliza has disappeared. Doolittle then joins them, magnificently attired in frock coat and top hat. He reveals that he has been left a fortune by an American millionaire with an interest in moral reform, to whom Higgins had facetiously described Doolittle as the most original moralist in England. Doolittle is not happy being rich—he yearns for his old, carefree life.

Eliza, who has been staying with Mrs. Higgins since her disappearance from Wimpole Street, enters the room. Her cool assumption of equality infuriates Higgins. Doolittle invites Mrs. Higgins and Pickering to attend his wedding, leaving Higgins and Eliza alone. They argue about Eliza’s future, and she says she will marry Freddy, a fate Higgins regards as a preposterous waste of his “masterpiece.” The act and the play end with Higgins instructing Eliza to buy various items for him, assuming that she will return to Wimpole Street. Eliza refuses, but Higgins expresses confidence that she will do as she is told.

The play is followed by a lengthy “sequel,” or an explanation of what Shaw believes would occur after the play, including Eliza’s marriage to Freddy.