Epistalory adventures in an alternate universe Regency!
Kate has gone to London for her Season because it's impossible to bring out her younger sister Georgina without her. Cecelia stays home in the country because it would be folly to unleash both her and her cousin on London at once. So they exchange letters about their lives. Kate writes of how she attended an investiture of the Royal Society of Wizard, found a mysterious doorway where a woman offered her hot chocolate, with rather menacing conversation, and made a shocking scene, and how, somwhat later, a marquise appears to dance with her at a ball and explain that he is the mysterious Thomas that the woman was talking of. Cecelia writes of how Lady Tarleton will have a ball for her niece, Dorothea, and how Dorothea instantly (and involuntarily) turns the head of every young man within hailing distance on arrival.
When Thomas asks Kate to marry him on the condition that she call it off, because she is the only woman in the ton who will not mistake him, and Cecelia finds that Lady Tartleton's son is spying on Dorothea, the plot thickens. Kate and Cecelia find their correspondence of great aid in unravelling the mystery, as no one is willing to tell them anything. It involves a man being turned into a tree, ducks, a non-existent fan, a form of black magic taught in a family, an elopement, and much local color in the Regency style.