How does the author use metaphor in the novel, The Ninth Hour?

The central metaphor of cleanliness is the laundry room, where Annie and Sally are taught by Illuminata how to clean and her vocation parallels a nun's purifying presence in the world. Clean linens or the scent of laundered clothes remind Sally of a nun's vocation and the order and purity of the convent. When she decides to abandon the idea of becoming a nun, she enters a worldly laundry room at a hotel. She uses alum and ammonia to cleanse the world from the elements that contribute to sin, mainly by murdering Mrs. Costello. The symbol of cleanliness is distorted and transformed into a noxious element, implying that good and evil are not discrete or absolute categories.