Henry Dashwood dies and, in accord with British custom and law, leaves his substantial estate and wealth to the oldest son of his first marriage, John Dashwood. This leaves his second wife, Margaret Dashwood, and her daughters, Elinor and Marianne, without a home and little income. Though John has pledged to his dying father to provide for his stepmother and stepsisters, he sidesteps his promise to do so. Mrs. Dashwood then accepts an offer from a distant cousin, Sir John Middleton, who has heard of her situation: with her daughters she moves to a small house in Barton Park, located in Devonshire. Nineteen-year-old Elinor is unhappy about leaving their Norland estate home because she has met and fallen in love with Edward Ferrars, the brother-in-law of her half-brother, John.
In their new home they encounter new acquaintances, including the retired officer (and bachelor) Colonel Brandon, and the magnetic and impetuous John Willoughby. Seventeen-year-old Marianne is utterly smitten with Willoughby, and it seems that he is equally passionate about her. Willoughby and Marianne become very attached, and it appears that their whirlwind romance will quickly result in an engagement; but Willoughby suddenly announces he must depart Devonshire for London with little explanation as to why. Marianne is inconsolable. Meanwhile Lucy and Anne Steele, two distant cousins of Lady Middleton’s mother, Mrs. Jennings, arrive at Barton Park as guests. Lucy is especially eager to meet Elinor and after ingratiating herself confides that she has been secretly engaged to Edward Ferrars for almost four years. Deeply shocked and distressed, Elinor nonetheless keeps her feelings to herself and—when pressed—agrees to keep Lucy’s secret until Miss Steele is able to meet and win over Edward’s imperious mother, Mrs. Ferrars.
Mrs. Jennings organizes a winter stay at her London home for Elinor and Marianne. Marianne continues to pine for Willoughby and hopes to meet with him in London. Colonel Brandon visits and tells Elinor that the talk in London society is of an engagement between Marianne and Willoughby. It is very clear by now that Colonel Brandon harbors his own feelings of deep attachment to Marianne. At a subsequent London party Marianne sees Willoughby, but he coolly rebuffs Marianne and rejoins his own friends, including Miss Sophia Grey. The next day a letter from Willoughby arrives for Marianne, and in it he disowns ever having had feelings for her. Shortly after, it is revealed that Willoughby is to be married soon to Miss Grey. It is then that Colonel Brandon informs Elinor of Willoughby’s history of debauchery, including with Brandon’s own adopted ward, Eliza.
Not long after this, Lucy’s sister Anne reveals news of Lucy’s secret engagement to Edward Ferrars. Outraged, Mrs. Ferrars disinherits Edward, and promises the family fortune will go to Edward’s brother Robert instead. The Dashwood sisters leave London to visit with family friends in Somerset, and it is there that the still grieving Marianne develops a severe cold that quickly worsens and threatens her life. Colonel Brandon, who had escorted the Dashwood sisters to Somerset, departs so that he might bring Mrs. Dashwood from Devonshire to Somerset. After Brandon leaves, Willoughby arrives seeking forgiveness from Marianne. Elinor denies him that privilege, and Willoughby makes an explanation of his actions to her. Elinor takes a level of pity on Willoughby, and he departs into the night. Marianne’s fever breaks, and when Mrs. Dashwood and Colonel Brandon arrive the next morning they are relieved to find Marianne beginning to recover.
Elinor later tells Marianne of Willoughby’s visit, and Marianne fully realizes that she could never have found happiness with him. As preparations are made for a return to Barton Park, Marianne begins to appreciate Colonel Brandon and finds herself increasingly attached to him. Brandon and Marianne soon become engaged to marry.
Shortly after the return to Barton, the Dashwoods learn from a servant that Lucy Steele has married Mr. Ferrars. Unsurprised at the news, they are nonetheless saddened to hear it. Edward arrives soon after and corrects a misconception: Lucy Steele has instead married the recipient of the family fortune, the supercilious younger brother, Robert. Edward confesses that he has loved Elinor and only Elinor ever since their first meeting at Norland and now he is finally free to propose to her. Elinor happily accepts and the story ends on a note of exhilarated joy.