Vienna, October 1767.
Out of ten children recorded in the death register, nine had died of smallpox.
The engaged princess Maria Josepha of Habsburg Lorraine, betrothed to Ferdinand IV of Bourbon king of Naples, contracts the disease and dies at sixteen.
All theaters in the Empire are closed for six weeks.
Leopold Mozart makes the decision to leave "this haunted city" and heads with his family to Olmütz, two hundred kilometers north.
After two days of travel, they arrive at their destination and take accommodation at the Black Eagle Inn.
The next day Wolfgang begins to sweat, his cheeks are red and hot, his hands cold, his pulse irregular.
On October 31, smallpox explodes: the fever becomes very high, the pustules cover him entirely, the body swells.
Wolfgang had not been given the vaccine although inoculation was already widespread: only prayer remained.
The terror lasts a week, then the fever goes down, the pustules dry up and disappear.
Wolfgang, eleven years old, gets up, looks in the mirror and exclaims: "I am looking like Mayr".
Andreas Mayr, Salzburg violinist with the pockmarked face of someone who has had smallpox.
Throughout the rest of his life Mozart will carry the signs of the disease.