Catherine Morland, an imaginative and unpretentious young woman from a clergyman's family in Wiltshire, is invited by wealthy neighbours, the Allens, to accompany them to the fashionable city of Bath. Unversed in the ways of high society, Catherine soon forms a close friendship with the superficial Isabella Thorpe, whose brother John pursues Catherine with boisterous persistence. More importantly, Catherine is introduced to Henry Tilney, a witty clergyman, and his gentle sister Eleanor, whose father, General Tilney, owns the imposing Northanger Abbey. Catherine's eager acceptance of an invitation to stay at the abbey unleashes her gothic fantasies, heavily influenced by her obsession with popular horror novels like The Mysteries of Udolpho.
Walking the ancient corridors, she begins to suspect the general of murdering or imprisoning his late wife, constructing elaborate plots of dark tyranny from ordinary domestic stiffness. When her suspicions are exposed by Henry, Catherine must confront the absurdity of her overactive imagination and the pain of misplaced trust, particularly after the Thorpe family reveals a mercenary and fickle nature. Through humiliation and reflection, Catherine learns to balance romantic fancy with sober judgment, eventually finding that real life offers its own quiet trials and genuine rewards.