Two Empresses centers around two young women who are cousins, Marie Josèphe Rose Tascher de La Pagerie and Aimée du Buc de Rivéry, growing up in Martinique. The story opens up in 1779, on an evening where Rose (who history would known as Joséphine) and Aimée sneak out of the house to go visit a mystic by the name of Euphemia David, a woman who is something of a local legend.