"Though the novel is named after the character Edwin Drood, it focuses more on Drood's uncle, John Jasper, a precentor, choirmaster and opium addict, who is lusting after his pupil, Rosa Bud.
La Cathédrale continues the story. After his retreat at a Trappist monastery, Durtal moves to the city of Chartres, renowned for its cathedral. Huysmans describes the building in great detail" -- Wikipedia.