and she mocks herself for not following the rules of composition:

Concerning the one [gentleman] in question, therefore, I have only to add — aware that the rules of composition forbid the introduction of a character not connected with my fable — that this was the very gentleman whose negligent servant left behind him that collection of washing–bills, resulting from a long visit at Northanger, by which my heroine was involved in one of her most alarming adventures. (Ch. 31)