Lady Susan Vernon, a beautiful and charming recent widow, visits her brother- and sister-in-law, Charles and Catherine Vernon, with little advance notice at Churchill, their country residence. Catherine is far from pleased, as Lady Susan had tried to prevent her marriage to Charles and her unwanted guest has been described to her as "the most accomplished coquette in England". Among Lady Susan's conquests in London is the married Mr. Manwaring. Catherine's brother Reginald arrives a week later, and despite Catherine's strong warnings about Lady Susan's character, soon falls under her spell.
Lady Susan is a short epistolary novel, possibly written in 1794 but not published until 1871.