Although a plain girl, Catherine Morland believes she is destined to become a heroine like those in her favorite gothic novels. She might, however, have spent her entire life in Fullerton, the small village in which she was born, had not Mrs. Allen, the wife of a wealthy neighbor, invited her to go to Bath. There a whole new world was opened to Catherine, who was delighted with the social life of the colony. At Bath, she meets Isabella Thorpe, who is more worldly than Catherine and takes it upon herself to instruct Catherine in the ways of society. Isabella also introduces Catherine to her brother, John Thorpe. He and Catherine’s brother, James Morland, are friends, and the four young people spend many enjoyable hours together.

Catherine meets Henry Tilney, a young clergyman, and his sister Eleanor, with whom she is anxious to become better acquainted. John thwarts her in this desire, and Isabella and James aide him in deceptions aimed at keeping her away from Henry and Eleanor. After Isabella and James are engaged, Isabella doubles her efforts to interest Catherine in her beloved brother. Although Catherine loves her friend dearly, she cannot extend this love to John, whom she knows in her heart to be an indolent, undesirable young man.

While James is at home arranging for an allowance so that he and Isabella can be married, Henry Tilney’s brother, Captain Tilney, appears on the scene. He is as worldly as Isabella and, even more important to her, extremely wealthy. Catherine is a little disturbed by the manner in which Isabella conducts herself with Captain Tilney, but she is too loyal to her friend to suspect her of being unfaithful to James.

Shortly after Captain Tilney arrives in Bath, Catherine is invited by Eleanor Tilney and her father, General Tilney, to visit them at Northanger Abbey, their old country home. Catherine is delighted; she always wanted to visit a real abbey. She quickly writes for and receives a letter of permission from her parents. Henry arouses her imagination with stories of dark passageways and mysterious chests and closets.

When the party arrives at Northanger Abbey, Catherine is surprised and a little frightened to find that the Tilney’s descriptions had been so exact. When she hears that Mrs. Tilney died suddenly several years previously, Catherine begins to suspect that the general murdered her. At the first opportunity, she attempts to enter the dead woman’s chambers. Henry finds her there and assures her that his mother died a natural death. Catherine is almost disappointed, for this news destroys many of her romantic imaginings about Northanger Abbey.

For more than a week after this event, Catherine worries because she receives no letter from Isabella. When a letter arrives from her brother, James, she learns the reason for Isabella’s silence. He wrote that Isabella was engaged to Captain Tilney. Catherine almost becomes ill when she reads the news, and Henry and Eleanor Tilney are as disturbed as she. They know that only greed and ambition drew Isabella from James to their wealthier brother, and they fear for his happiness. They believe, however, that the captain is more experienced with such women and will fare better than had James.

Shortly afterward, Catherine receives a letter from Isabella telling the story in an entirely different light. She pretends that she and James had just had a misunderstanding and begs Catherine to write to James in her behalf. Catherine is not taken in. She wastes no time in sympathy for her onetime friend and believes her brother fortunate to be rid of such a schemer.