Country gentleman Henry Dashwood dies, unable to pass on the estate where he lived with his second wife and their three daughters. Norland Park is entailed to be inherited through the male line to John Dashwood, Henry's son by his first marriage, and thence to Harry Dashwood, the four-year-old son of John. On his deathbed, Henry extracts a promise from John to take care of his half-sisters, Elinor, Marianne, and Margaret. But John's wife, Fanny, persuades her husband to renege on the promise, appealing to his concerns about diminishing his own son Harry's inheritance, despite the fact that John is already independently wealthy and owns another lavish home in London. Henry's love for his second family is also used by Fanny to arouse her husband's jealousy, and persuade him not to help his sisters financially. He gives them nothing and the family must decide how to survive on a pitifully small income.
John and Fanny move in as the new owners of Norland Park, where the Dashwood women are treated as unwelcome guests by Fanny. Mrs. Dashwood urgently seeks somewhere else to live. Meanwhile, Fanny's brother, Edward Ferrars, visits Norland and his kindness immediately endears him to the Dashwood family. Although their attraction is palpable, Edward and Elinore's budding romance is never spoken of directly between them, but others take notice. Fanny offends Mrs. Dashwood by implying that Elinor is unworthy and must be motivated by his expectations of coming into money.
Mrs. Dashwood moves her family to Barton Cottage in Devonshire, on the estate of her cousin, Sir John Middleton. Their new home is modest, but they are warmly received by Sir John and welcomed into local society, meeting his wife, Lady Middleton, his mother-in-law, the garrulous but well-meaning Mrs. Jennings, and his friend, Colonel Brandon. Colonel Brandon is attracted to Marianne, and Mrs. Jennings teases them about it. Marianne is irritated by her meddling, as she considers the thirty-five-year-old Colonel Brandon an old bachelor, incapable of falling in love or inspiring love in anyone.
A 19th-century illustration by Hugh Thomson showing Willoughby cutting a lock of Marianne's hairWhile out for a walk, Marianne gets caught in the rain, slips, and sprains her ankle. John Willoughby sees the accident and assists her, picking her up and carrying her to her home. Marianne is dazzled by his good looks and similar tastes in poetry, music, art, and romance. His frequent attentions and Marianne's effusive behavior lead Elinor and Mrs. Dashwood to suspect that the couple are secretly engaged. Elinor cautions Marianne against her unguarded conduct, but Marianne refuses to check her emotions. Willoughby engages in several intimate activities with Marianne, including taking her unchaperoned to see the home he expects to inherit one day and obtaining a lock of her hair. When the announcement of an engagement seems imminent, Willoughby instead informs the Dashwoods that his aunt, upon whom he is financially dependent due to his debts, is sending him to London on business, indefinitely. Marianne is distraught and Elinore and Mrs. Dashwood are confused and disappointed.
Edward Ferrars pays a long-awaited visit to Barton Cottage, but seems unhappy. Elinor fears that he no longer has feelings for her, but she will not show her heartache. After Edward departs, sisters Anne and Lucy Steele, vulgar cousins of Mrs. Jennings, come to stay at Barton Park. Lucy informs Elinor in confidence of her secret four-year engagement to Edward Ferrars that started when he was studying with her uncle. Elinor realizes Lucy's visit and revelations are the result of her jealousy and cunning calculation. This helps Elinor understand Edward's recent sadness and behavior towards her. She acquits Edward of blame and pities him for being held to a loveless engagement to Lucy. Lucy extracts an unnecessary promise to keep her secret, which honor would have forbidden Elinor to speak of in any case.
Elinor and Marianne accompany Mrs. Jennings to London. On arriving, Marianne writes several personal letters to Willoughby, which go unanswered. When they meet by chance at a dance, Willoughby is with another woman. He greets Marianne coldly, to her shock and disbelief. Elinor guides her from the party, hardly able to walk. Soon Marianne receives a curt letter enclosing their former correspondence and love tokens, including the lock of her hair. Willoughby is revealed to be engaged to Miss Grey, a young lady with a large fortune. Marianne is devastated. After Elinor reads the letter, Marianne admits to her that she and Willoughby were never actually engaged. She behaved as if they were because she knew she loved him and thought that he loved her.
As Marianne grieves, Colonel Brandon visits and reveals to Elinor that Willoughby seduced and abandoned Brandon's young ward, Miss Eliza Williams, who has his child. Willoughby's aunt subsequently disinherited him, and so, in great personal debt, he chose to marry Miss Grey for her money. Eliza is the natural daughter of Brandon's first love, also called Eliza, a young woman who was his father's ward and an heiress. She was forced into an unhappy marriage to Brandon's elder brother, in order to shore up the family's finances, and that marriage ended in scandal and divorce while Brandon was abroad with the Army. After Colonel Brandon's father and brother died, he inherited the family estate and returned to find Eliza dying in a pauper's home, so Brandon took charge of raising her young daughter. Brandon says Marianne strongly reminds him of the elder Eliza for her sincerity and sweet impulsiveness. Brandon removed the younger Eliza to the country, and reveals to Elinor all of these details in the hope that Marianne could get some consolation in discovering Willoughby's true character.
Meanwhile, the Steele sisters have come to London. After a brief acquaintance, they are asked to stay at John and Fanny Dashwood's London house. Lucy sees the invitation as a personal compliment, though it is actually a slight to Elinor and Marianne who, being family, should have received such an invitation first. Fanny's mother, Mrs. Ferrars, is invited to dine with the family and their guests; during the dinner, she is rude to Elinor while being relatively warm towards Lucy. Afterwards, Anne believes that the Ferrars family as a whole has become fond enough of Lucy to welcome her into the family, and betrays to Fanny Lucy's secret engagement to Edward Ferrars. As a result, the sisters are turned out of the house, and Edward is ordered by his wealthy mother to break off the engagement on pain of disinheritance. Edward, still sensitive of the dishonor of a broken engagement and how it would reflect poorly on Lucy Steele, refuses to comply. He is disinherited in favor of his brother, Robert, which gains Edward respect for his conduct and sympathy from Elinor and Marianne. Colonel Brandon shows his admiration by offering Edward the clerical living of a nearby parsonage, to enable him to marry Lucy after he is ordained. Marianne finally understands the silent heartache her sister has been enduring for the sake of self-respect and honor, in contrast with her own reckless behavior.
Mrs. Jennings takes Elinor and Marianne to the country to visit her second daughter, Mrs. Charlotte Palmer, at her husband's estate, Cleveland, on their way back to their home in Devonshire. Marianne, still in misery over Willoughby's marriage, goes walking in the rain and becomes ill. She is diagnosed with putrid fever, a highly contagious disease, and it is believed that her life is in danger. Everyone evacuates the house but Elinor and the doctor. Elinor writes to Mrs. Dashwood to explain the gravity of the situation, and Colonel Brandon volunteers to go and bring Marianne's mother to Cleveland to be with her. In the night, Willoughby arrives and reveals to Elinor that his love for Marianne was genuine and that losing her has made him miserable. He also reveals that his aunt said she would have forgiven him if he married Miss Williams but that he had refused. He elicits Elinor's pity, but she is disgusted by the callous way in which he talks of Miss Williams, his abandoned child and his wife.
Marianne recovers from her illness, and Elinor tells her of Willoughby's visit. Marianne realizes she could never have been happy with Willoughby's immoral, erratic, and inconsiderate ways. She values Elinor's more moderated conduct with Edward and resolves to model herself after her courage and good sense. Edward later arrives and reveals that, after his disinheritance, Lucy jilted him and married his now wealthy younger brother, Robert. Elinor is overjoyed. Edward and Elinor marry, and later Marianne marries Colonel Brandon, having gradually come to love him. The two couples live as neighbors, with sisters and husbands in harmony with each other. Willoughby considers Marianne as his ideal but the narrator tells the reader not to suppose that he was never happy.
