Rosi Holzwurm, a cleaning lady in Limone sul Garda, discovers a viola belonging to a violin maker named Gasparo da Saló at her client Otto Simon's place. Simon asks Rosi in an accompanying letter to return the instrument to an elderly lady, but the old woman is in the hospital following a brutal accident. Shortly after, Simon is found dead in Lake Garda. Why did he have to die? And why is Rosi being pursued by a dubious janitor and an opaque antique dealer from Malcesine? When Rosi realizes that certain people will go to great lengths for this viola, it is almost too late.