Twin cases of mistaken identity activate the plot of Northanger Abbey. Escorted to Bath by a kindly Mr and Mrs Allen, the heroine promptly gets mistaken for the Allen heir. In turn, the Allens, a modestly-well-to-do country couple, are thought vastly rich. These catalysts for Austen's plot have never been investigated with an eye to an historical explanation, because being mistaken for an heiress neatly fits the Gothic model that Northanger Abbey decidedly spoofs. But Austen's fiction has an unacknowledged basis in historical fact, characteristically offering her peculiar brand of hyperrealism as a retort to the Gothic novel. In reality, Bath's largest private fortune, belonging to a genuine Mr and Mrs Allen, was in transition during precisely the years that Austen drafted her novel (Cassandra dated it to 1798 and 1799). The wealth amassed by Bath entrepreneur Ralph Allen (1693–1764), and held by a niece for over three decades, was just then reverting to obscure Allens living in the country. These historical circumstances warrant a fresh look at Northanger Abbey, where the many encoded references to Ralph Allen's architectural legacy reveal a historical specificity to Austen's method that rivals the cartographic exactitude of James Joyce.