The Flame Is Love by Barbara Cartland

Reluctant to accept her arranged marriage to an English Duke she has never met, beautiful young American oil heiress, Emmeline Nevada Holtz, nicknamed ‘Vada’ after the State, travels to Paris to buy her trousseau before meeting her husband-to-be. When her travelling companion, Nancy Sparling, has an accident and hurts her leg, Vada assumes her name to avoid unwelcome attention and travels on with just her elderly maid, determined to make the most of her last chance to explore Bohemian Paris and the wonders of the City that she had heard and read so much about. At her hotel she finds a handsome intruder in her suite, not a thief as she at first thinks but a journalist looking to interview the famous heiress Emmeline. Smitten by this charismatic Frenchman and his talk of poetry, Vada finds herself agreeing to go with him to the Soleil d’Or, wellspring of the Symbolist movement. Soon they are deeply and uncontrollably in love, a love that is surely doomed by her deception, her betrothal to the Duke and now a terrifying ordeal at a Satanist Black Mass on the dark side of the City of Light.