Emma Woodhouse 21 years old lives with her widowed father on their estate Hartfield. They are at the upper rung of the social ladder in her eyes. Her governess Miss Anne Taylor has just married, and now lives happily with Mr. Weston at their estate Randalls. Emma believes she arranged this marriage. Her older sister Isabella has previously married John Knightley and they live in London with their 4 children.
Perhaps out of boredom, Emma decides to take Harriet Smith underwing and arrange a match for her. Harriet is c. 18 and of unknown parentage, lives at Mrs. Goddard's boarding school. Emma disapproves of Mr. Robert Martin, a tenant farmer who proposes to Harriet, and dissuades her from him. Emma's long-time neighbor and wise older friend. Mr. Knightley chastises her for her manipulations, insisting that Mr. Martin is of higher class than Harriet and would have been a good match.
She tries instead to get Harriet and the vicar Mr. Elton matched, for example by painting Harriet's likeness in front of Elton. Elton delivers a charade about courtship which Emma thinks is directed to Harriet. But her plans backfire and Elton instead declares his love for Emma while they are alone in a carriage, returning from a Christmas Eve dinner at the Weston's-- much to her displeasure and Harriet's subsequent distress.
Mr. Weston's son from his first marriage, Frank Weston Churchill, has been essentially adopted by the wealthy brother of his deceased first wife Mr. Churchill and his domineering wife Mrs. Churchill, living at their estate Enscombe. She kept Frank from paying adequate attention to his father, even after Mr. Weston's remarriage, and Mr. Knightley criticizes Frank's character and lack of a sense of duty to his father.
Jane Fairfax is an orphan, the only child of Mrs. Bates' youngest daughter Jane and Lt. Fairfax. After her father's death, she was taken into the family of Colonel & Mrs. Campbell, who felt indebted to Lt. Fairfax and also desired Jane as a companion to their own now-married daughter Mrs. Dixon. Jane now arrives for an extended visit with Mrs. Bates and her daughter (Jane's Aunt), the garrulous Miss Bates, while the Campbells are vacationing with the Dixons in Ireland. Emma speculates with Frank that there was a relationship between Mr. Dixon and Jane. Frank drives 32 miles for a haircut, wants to have a ball, and seems very "gallant", in contrast to the understated Mr. Knightley, who disapproves.
Mr. Elton returns from Bath with a fiancée, Miss Augusta Hawkins, an upwardly mobile and rather vulgar woman who does not please Emma. At the Coles' dinner party, the piano sent to Jane from an unknown donor is discussed. Mrs. Weston is plotting a match between Jane and Mr. Knightley, which Emma discourages. Frank and Emma dance. Emma plays the piano followed by Jane, and Knightley rescues Jane from the overexertions at singing urged by Frank.
The Weston's inform Emma that Frank and Jane are now engaged and in fact have been secretly engaged since last October, before she came to Highbury, and Frank is roundly criticized for his deception.
Harriet tells Emma that she loves Knightley-- Emma suddenly realizes her own love for him and laments the possibility of losing him. Mr. Knightley returns from a visit to London, consoling Emma mistakenly thinking she was in love with Frank. When she denies this, he declare his love for her. Emma and Knightley decide to live with her father at Hartfield as long as he lives.
Harriet goes to visit the John Knightleys in London and becomes engaged to Mr. Martin after all, about which Emma is pleased. Harriet marries in September and Frank and Jane will marry in November. Emma and Mr.Knightly marry in October.