Preface – The author explains the purpose of the play: to show how phonetics can lift a common “flower girl” into a respectable lady and to promote the importance of the phonetics profession.

ACT I – Covent Garden, stormy night. A mother and her daughter wait for a cab; their chauffeur Freddy fails to find one and collides with a ragged flower‑girl (Eliza Doolittle). Their exchange, written in exaggerated Cockney, draws a crowd that includes a military gentleman, a sarcastic by‑stander and a “note‑taker” who records Eliza’s speech. The rain stops and the crowd disperses.

ACT II – The next morning in Professor Henry Higgins’s phonetics laboratory on Wimpole Street. Colonel Pickering is present among scientific apparatus. Mrs. Pearce tells Higgins a “common” young woman wants to see him. Higgins reluctantly admits the flower‑girl, now called Eliza Doolittle. She demands payment; Higgins offers a shilling, while Pickering wagers that Higgins cannot teach her to speak like a duchess in three months. Higgins accepts the bet, promising to turn her into a lady, and begins phonetic transcription of her speech.

ACT III – Mrs. Higgins’s at‑home day. Higgins arrives uninvited, quarrels with his mother about staying, and then brings the “experiment” – Eliza – to the drawing‑room. Eliza arrives impeccably dressed, having been transformed by Higgins’s lessons. She meets the Eynsford Hills (mother and daughter) and Freddy, who recognize her from Covent Garden. A series of small‑talk exchanges reveal Eliza’s new pronunciation, her lingering Cockney idioms, and the awkwardness of her social integration. The gathering shows the contrast between her polished speech and the lingering class prejudices of the guests.

ACT IV – Midnight in the drawing‑room. Higgins and Pickering discuss the evening’s garden‑party success while Mrs. Pearce prepares for bed. Dust‑man Alfred Doolittle, Eliza’s father, arrives demanding his daughter. He explains that a wealthy American benefactor (Ezra Wannafeller) has left him a modest annual income on condition he lecture for a moral‑reform society. Higgins begrudgingly pays Doolittle five pounds. Later, Eliza returns, now elegant, and confronts Higgins about her future, the ownership of her clothes and jewellery, and the cruelty of treating her like a laboratory specimen. She throws his slippers at him, demands she may keep what she has earned, and threatens to leave. Higgins attempts to placate her with vague promises of employment, but Eliza remains defiant.

ACT V – Mrs. Higgins’s drawing‑room later that morning. Mrs. Higgins discovers that Eliza has left, learns from Mrs. Pearce that Eliza complained of “brutal” treatment. Pickering arrives; they consider calling the police. Alfred Doolittle re‑enters, now richly dressed, insisting that the inheritance obliges him to provide for his daughter. He declares he will support her financially. After heated exchange, Mrs. Higgins suggests offering Eliza a night’s shelter. Eliza returns, composed, greets the household politely, and announces she will not marry Professor Higgins. She accepts Freddy Eynsford Hill’s proposal, stating they will marry and build a modest life together. Higgins reacts bitterly, remarking that Eliza will be a “duchess” in six months, while he is left alone, reflecting on his experiment and the loss of his “creation.”