From the Book's Opening Paragraph:
Welcome to "Siren's Song," the fourth installment of the Gloria Mundi chronicle for Mage: The Awakening. In this story, the characters begin their own investigation of the Vice-spirits and discover that one of them, at least, has carved out a niche for itself in the Fallen World. They find out how subtle and poisonous the influence of these spirits can be, and, hopefully, they learn that diplomacy can be just as effective a tool for banishing the spirits as brute force and magical prowess.
Along the way, the characters also discover that even in a city with Puritanical roots, the pleasures of the flesh make for popular pastimes. The rich and jaded take these pastimes to extremes... and the spirit of Lust is soaking up their carnal excesses.