A possessive son's efforts to keep his mother from remarrying threaten to destroy his family.

In 1873, in a small Midland town, the magnificence of the Ambersons, the town's wealthiest family, dominates the social scene. The denizens are abuzz with the news that Isabel Amberson, the daughter of the family, has jilted her suitor, Eugene Morgan, because he embarrassed her by becoming tipsy and stepping through a bass violin. After Isabel spurns Gene for the more prosaic Wilbur Minafer, the couple are married and bear a son, George Amberson Minafer. Isabel pours all the love that she felt for Gene into George, and consequently the boy develops into a spoiled enfant terrible . He soon engenders the enmity of all the townspeople, who eagerly anticipate the boy's "comeuppance." Years later, George comes home from college for the holidays and his family stages one of the last great balls in his honor. Gene, now widowed, returns to town after a long absence and attends the dance with his daughter Lucy. George, enchanted by Lucy and unaware of her father's former romance with his mother, asks her to dance. When Lucy tells George that her father, an inventor, is developing a horseless carriage, George ridicules the idea, causing Lucy to comment on the boy's self-important attitude. After George declares that his goal in life is to become a yachtsman, Lucy criticizes his lack of ambition. At the end of the evening, George voices his animosity toward Gene and teases his spinster aunt Fanny about pursuing the widower. The next afternoon, George invites Lucy on a sleigh ride. When their sleigh overturns, spilling them into the snow, Gene gives them a ride home in his horseless carriage. Some time later, Wilbur, who has become depressed over a series of bad investments, dies. Unmoved by his father's death, George returns from school and continues to taunt Fanny about her romantic interest in Gene. As the Ambersons' fortune declines, Gene's auto factory becomes a financial success. While seated in the arbor with Isabel one day, Gene, who has never stopped loving her, begs her to tell George about their love for each other, but Isabel is afraid to incur her son's disapproval. Later, George proposes to Lucy, and when she rejects him because of his lack of ambition, George blames Gene for Lucy's opinions. After Lucy leaves town to visit a friend, the Ambersons invite Gene to dinner. When the discussion turns to the way in which Gene's horseless carriage will revolutionize civilization, George denounces the automobile as a nuisance. After dinner, Fanny praises George for defending his mother's reputation by being rude to Gene. When Fanny tells George that the entire town has been gossiping about Gene's courtship of Isabel, the boy becomes furious. The next day, when Gene comes to take Isabel for a drive, George refuses to let him see his mother and slams the door in his face. Shocked by George's behavior, Jack, Isabel's brother, escorts his sister into the dining room for a private conference to discuss his nephew's conduct, while George and Fanny bicker on the staircase. Afterward, in a letter to Isabel, Gene confides his fear that George will never accept their marriage and presses her to choose between her true love and her son. Although torn, the always-devoted mother Isabel chooses her son. When Lucy returns home, George informs her that he and his mother are leaving on an around-the-world trip and he may never see her again. Lucy feigns indifference, but once George walks away, she faints. Some time later, Jack returns home from Paris after visting his sister and George. He confides to Gene that although Isabel is gravely ill, George will not allow her to leave Europe. When Isabel, now an invalid, returns home to die, Gene comes to see her but is turned away by her family because she is too sick for visitors. As George holds his mother's hand at her deathbed, Isabel, with her dying words, expresses her desire to see Gene one last time. Soon after, Isabel's father, Major Amberson, devastated by his daughter's death and family's dwindling fortunes, dies. Penniless, Jack says goodbye to George and leaves town to accept a job elsewhere. Gene, now accompanied by Lucy, returns to the arbor where Lucy recalls the legend of a brash young Indian chief who was exiled by his tribe for his odious conduct. Destitute, George finds employment as a low-paid clerk in a law office. When Fanny, in a hysterical fit of self-pity, insists on moving into an expensive boardinghouse, however, George quits his job to take higher paying work in a dynamite factory. On the day before he is to move out of the family mansion, George visits his deceased mother's empty bed and preys for forgiveness. Afterward, he is struck by a car and hospitalized. When Lucy reads the news of George's accident, she insists on going to him at the hospital and Gene follows. In the corridor outside George's room, Gene tells Fanny that Lucy's presence has restored George's will to live and that George has extended his hand and asked for forgiveness. Gene then confides that he felt Isabel's presence in George's hospital room and that by offering her son refuge, he was being true to his undying love for her.