The Guardian summarized the plot of the book as follows:

When Mozart dies, six weeks after telling his wife that he has been poisoned, his estranged sister Nannerl turns detective, scrutinising old scores, journals and the like, until she discovers Wolfgang's role in a vast Masonic conspiracy. Did the composer encode his final opera, The Magic Flute, with the secrets of his own demise?... Rees says he used "meditation and concentration techniques" to think his way into the lives of Nannerl and Wolfgang, and based the plot structure on Mozart's Piano Sonata in A minor.

Though most historical experts think that Mozart died of rheumatic fever, Mozart’s Last Aria seems to be one more take on Mozart’s dramatic life story.

To see Kevin Sullivan’s in-depth documentary about the life of the composer, click here.