Using dramatization, performance and documentary, the opera singer Thomas Allen argues that the key to understanding Mozart's demonic philanderer is through Giacomo Casanova.

Whilst performing the role in contemporary Prague, Allen sets out to prove that the real-life eighteenth century sex maniac was not only a direct influence on Mozart's opera, but that he was involved in its creation. Before long, Allen becomes caught up in the romance of performing this role, and his obsession begins to slip into fantasy.