Upon his father's death, Mr. John Dashwood inherits Norland, his family's estate. Although he has promised his father to be generous to his stepmother and three stepsisters, Mr. Dashwood's wife, Fanny, convinces him to significantly lower his generosity. His father's family is given only 500 pounds each.
Fanny immediately descends on Norland to take on her role as mistress of the estate. Mrs. Dashwood and her three daughters, Elinor, Marianne and Margaret, must find a new home. Before they leave Norland, Fanny's brother Edward arrives for a visit. He and Elinor form a particular attachment, but Fanny advises Mrs. Dashwood that her mother would not approve of Elinor because of her now meager station. Mrs. Dashwood accepts an offer from a distant cousin, Sir John Middleton, to reside on his estate in Devonshire in a small house named Barton Cottage.
The Dashwood women bid a tearful farewell to Norland before setting off for Barton Cottage. Sir John Middleton welcomes them affectionately and promptly insists that they dine with him and his family at Barton Park. Although he is warm and friendly, his wife is rather distant and quiet. Their four children are spirited, and the Dashwoods are soon overwhelmed by them. Mrs. Middleton's mother, Mrs. Jennings, is a regular visitor to Barton, but her nosiness and tendency to gossip do not make her a favorite among the Dashwoods. Another guest, Colonel Brandon, is more reserved and cultured. He is obviously enraptured by Miss Marianne's beauty and musical ability, but she thinks he is too old at 30 to be thought of as a possible husband.
Miss Marianne is smitten, however, by the attentions of a dashing gentleman named Willoughby, who carries her home one afternoon after she injures her ankle. Sir John tells the Dashwoods that Willoughby is a fine gentleman, who is to inherit a wealthy aunt's estate. Marianne and Willoughby soon form a romantic attachment, much to Elinor's dismay. She feels her sister is acting without caution since they know so little of Willoughby's character. Elinor also doesn't care for Willoughby's dislike of Colonel Brandon, who has never acted in a rash or uncouth manner. Margaret informs Elinor that she spied Willoughby cutting off a lock of Marianne's hair and hiding it in his breast pocket. Elinor hopes the two have made a secret engagement but wonders that they have not announced their intentions.
Colonel Brandon invites his friends to a relative's home in the country for a picnic, but on the day of the excursion, receives a mysterious message that prompts him to leave for London. Since they cannot attend the picnic without him, the friends decide to ride about the country in their carriages. Marianne later admits to Elinor that Willoughby took her to Allendale, even though his aunt was not present. Elinor is shocked at her impropriety, but Marianne insists she is above reproach.
A few days later Mrs. Dashwood and Elinor arrive home to find Willoughby at the cottage and Marianne in tears. When pressed for an explanation, Willoughby apologizes that he can't stay for the extended dinner invitation and must instead make for London. He has no idea when he will return. Mrs. Dashwood is convinced he left because he wishes to keep his engagement to Marianne a secret from his aunt. Elinor suspects no such agreement exists between Willoughby and her sister. Marianne cannot eat or sleep because of her sadness.
Edward Ferrars arrives at Barton Cottage for an unannounced visit. At first, he is cold and formal to Elinor and Marianne but soon relaxes in their company. Marianne notices he has a locket ring with a lock of hair; she suggests that it is Elinor's, but he insists it is a lock of Fanny's hair. After a week, Edward begs his leave from them. Elinor convinces herself that he must have to perform some duty for his demanding mother.
Sir John arrives to tell the Dashwoods that they must attend dinner at Barton Park and meet his wife's sister, Charlotte, and her husband, Mr. Palmer. Charlotte is as talkative as her mother and is expecting her first child. Mr. Palmer is droll and spends all his time reading the newspaper. Charlotte attempts to get the Dashwoods to visit her house in the country. It is close to Willoughby's estate of Combe Magna, though he is rarely at home. Charlotte also tells Elinor that she recently saw Colonel Brandon in London. He informed her of Willoughby and Marianne's engagement. Elinor assures her that they have made no such announcement. Charlotte also reminisces that Colonel Brandon once wanted to marry her, but her parents wouldn't allow the match. Elinor doubts the truth of her claim.
After the Palmers leave Barton Park, Sir John invites two cousins, the Steeles, to visit. Although he praises the Steeles to the Miss Dashwoods, Marianne and Elinor are not impressed. The Steeles overly indulge the Middletons' children and talk too much of meeting eligible men in the area. Several days later, Lucy Steele surprises Elinor by asking if she has ever met Mrs. Ferrars, Edward's mother. Lucy admits that she and Edward have been secretly engaged for years and that Edward carries a lock of her hair in a ring. She begs Elinor to keep her confidence. Elinor is heartsick at the news.
Elinor convinces herself that although Edward may have an engagement with Lucy, it was made when he was younger and more foolish. She cannot believe that the Edward she knows could form an attachment with such an insipid individual as Lucy. The Steeles are disappointed that Elinor and Marianne will not spend time in London. Miss Jennings, however, soon amends that by offering an invitation for the Dashwoods to stay at her home in the city. At first they decline, but their mother insists they go with Miss Jennings. Elinor dreads the idea of running into Lucy and Edward, while Marianne is giddy with the thought of seeing Willoughby again. Upon arriving in London, Elinor writes to their mother while Marianne writes to tell Willoughby of her arrival. She is upset when no answer comes until Miss Jennings remarks about the weather. Marianne believes it may be keeping him out in the country.
Mr. and Mrs. Middleton arrive and host a ball. The Palmers and the Dashwoods attend, but Marianne is unable to enjoy herself because Willoughby is not in attendance. When they return home, Miss Jennings informs her that Willoughby was invited but refused to attend. Marianne is heartbroken. Colonel Brandon visits and tells Elinor that he has heard of Marianne and Willoughby's engagement. Elinor explains that she has heard nothing official from either of them but that she is sure of their mutual affection for each other. Colonel Brandon leaves, wishing Marianne all happiness.
Elinor and Marianne attend a social function with the Middletons, only to discover Willoughby is present. Marianne tries to engage him in conversation, but he won't meet her eyes. She asks if he received her letters. He admits he has, but she was not at home the one time he tried to visit. Leaving Marianne's company, he then stands with another woman, Miss Sophia Grey. Disheartened, Marianne and Elinor return to Miss Jennings' house. Marianne writes another note to Willoughby. He replies the following day, begging her forgiveness if he ever led her to believe their relationship was any more than an acquaintance. He is engaged to Miss Grey. He also returns her letters and the lock of hair he took from her at Barton Cottage. Elinor is appalled that Marianne was so forward in her affections when there was no promise made on his part. Marianne argues that though he never said it, she knew Willoughby loved her. Miss Jennings tries to raise Marianne's spirits with a dinner party, but to no avail. Marianne leaves for her room. Elinor remains behind and hears how Willoughby squandered his fortune and must marry Miss Grey to pay his debts.
Colonel Brandon returns the following day to tell his story to Elinor in hopes it may help alleviate some of Marianne's suffering. Many years ago, he loved a young woman named Eliza, but she was married to his older brother in order to ensure his family inherited her family's money. His brother was cruel, and Eliza eventually was unfaithful to him. The two divorced. Eliza disappeared for several years. Brandon found her dying of consumption. He promised to take care of her young daughter after her death. He placed the girl in a boarding school and often visited her. She disappeared a year earlier. Brandon received news of her whereabouts on the day of his previously planned picnic at his relative's home. He discovered that his ward had been seduced and abandoned by Willoughby. Mrs. Dashwood writes to her daughters, heartbroken over Willoughby's betrayal. She encourages them to stay in London, however, as their stepbrother and Fanny will be arriving soon.
The Dashwoods continue to stay in London, attending a dinner party at John and Fanny's house, where they are introduced to Edward's mother, Mrs. Ferrars. They find her proud and spiteful. Colonel Brandon also attends. John hopes that Elinor will marry Colonel Brandon, but although she esteems him, she knows his heart is still with Marianne. Mrs. Jennings is called away to attend to her daughter, Charlotte, who is ready to give birth. Lucy Steele visits after the party and regales Elinor with how charming Mrs. Ferrars had been to her. Edward arrives unexpectedly, and Marianne, ignorant of Edward's engagement to Lucy, tries to get him to compliment Elinor. Edward and Lucy soon make their exit, and Marianne wonders aloud why Lucy visits often, as no one really likes her. Elinor keeps Lucy's confidence. While attending a concert, Elinor is introduced to Edward's brother, Robert. She finds him as obnoxious and proud as his mother. Sir John wants to ask his stepsisters to stay at his house for a visit, but Fanny tells him she's already extended an invitation to the Steele sisters. Elinor wonders if this means Fanny knows of Lucy's engagement and hopes to woo her mother to Lucy's side.
Mrs. Jennings returns from a social visit with news that Lucy has made her engagement to Edward public. Fanny is beside herself with the news and has thrown Lucy out of her house. Mrs. Ferrars demands that Edward break his engagement, but he refuses. She then bequeaths her estate to his younger brother, Robert. Edward is left with a paltry sum. He must obtain a curacy in order to make a living. By letter, Lucy informs Elinor that she plans on sticking by Edward even during this dreadful time. Colonel Brandon tells Elinor to extend his offer of the curacy at his Delaford estate to Edward. Elinor begins to write a letter, but Edward arrives at Mrs. Jennings' house for a visit. Elinor tells him of Colonel Brandon's offer. Edward is overcome with gratitude. Elinor and Marianne leave London, stopping at the Palmers' estate as they make their way to Barton Cottage. Marianne takes several long walks and contracts a cold. She soon develops a serious fever. Elinor and Mrs. Jennings attempt to nurse her back to health. When she calls out for her mother, Colonel Brandon offers to ride to Devonshire and bring her back. While he is gone, Willoughby arrives. He begs Elinor's forgiveness and tells her that he truly loved Marianne. It is only that his debts have forced him to marry for money rather than love. Elinor is moved by his confession and promises to tell her sister. Marianne recovers from her illness. Mrs. Dashwood tells Elinor that in the carriage Colonel Brandon confessed his love for Marianne. Mrs. Dashwood will do what she can to encourage the match to her daughter.
Once back at Barton Cottage, a servant announces that he's seen Mr. Ferrars and his new bride. Both Marianne and Elinor are upset. Several days later, Edward arrives at Barton Cottage. It is soon discovered that Edward is not married. Lucy transferred her affections to his brother, Robert, who would be rich. Elinor is overcome with emotion. Edward asks for her hand in marriage, and she agrees. Colonel Brandon again offers the parsonage in Delaford to Edward. After their marriage, Edward and Elinor often ask Colonel Brandon and Marianne to visit in hopes that they will form an attachment. Their scheme works, and the Colonel and Marianne also reside at Delaford. The former Dashwoods often visit their mother and Margaret at Barton Cottage.