Toby is the orphaned nephew of the Theo Trentham, leader of a motley, down-at-heel troupe of actors touring Louisiana. They had hoped for great things in New Orleans during the Carnival. Instead a spiv has taken their money but booked them remote venues in the countryside. On Christmas Eve, the company straggle away from yet another seedy, unwelcoming town and are caught in a rainstorm. They shelter in a crumbling mansion named Illyria, occupied only by an enigmatic black woman, Marie LaRoche, and her mistress, a spirited Creole girl, Isabelle de Castelon. Toby falls desperately and instantly in love. But as Toby unravels the mysteries of Isabelle's origins, he begins to suspect something terrible will engulf them all. As the days gather pace towards the Mardi Gras festivities, magic, secrets, masks and disguises all come to a dangerous head.