It's February, and Carnival time in Venice. Bright blue skies and freezing temperatures welcome Teresa Lupo, forensic pathologist to the Rome Questura, to the city. She is greeted off the vaporetto by an anonymous masked man dressed as The Plague Doctor. Teresa has taken time out from her job to find her beloved bohemian aunt Sofia who has mysteriously disappeared. There seem to be no clues as to her whereabouts, but a visit to Sofia's very strange apartment in the Dorsoduro confirms Teresa's suspicions that all is not well.
The puzzle deepens when a letter reveals a piece of fiction in which both Sofia and Teresa appear. Even more strange, are the links to Venetian culture which gradually begin to surface. Are the messages being sent by Sofia herself? Her abductor? Or a third party seeking to help her unravel the mystery? The revelation when it comes is as surprising and shocking as Sofia's fate. And Teresa herself comes to depend upon the unravelling of a mystery wrapped deep inside the art and culture of Venice itself.