The year is 1312. The scene of the crime is Prato. Musciattino, from neighbouring Pistoia, sneaks into the Cathedral of Santo Stefano late at night, intent on stealing the city’s most prized possession: the relic of Mary’s girdle. But so strong is the faith of the pratesi that a mysterious fog descends outside, blurring the thief’s vision as he attempts his getaway and ultimately finds himself back where he started. Quickly discovering the deceit, the citizens call for his right hand to be severed and for him to be burned at the stake.