A speculative account of Maria Anna "Nannerl" Mozart (Marie Feret), five years older than Wolfgang (David Moreau) and a musical prodigy in her own right.

Originally the featured performer, she has given way to Wolfgang as the main attraction, as their strict but loving father Leopold (Marc Barbe) tours his talented offspring in front of the royal courts of pre-French revolution Europe.

Approaching marriageable age and now forbidden to play the violin or compose, Nannerl chafes at the limitations imposed on her gender.

But a friendship with the son and daughter of Louis XV offers an alternative.