Prudence Rutherford, a wealthy socialite from Secret of the Scarlet Hand, recommended Nancy Drew to the Italian Police (the Gdif) to investigate a series of art thefts happening in Venice. A Crime Syndicate is actually responsible for the thefts, using the names of the commedia dell'arte characters. Nancy is sent to spy on the ring and discover who is Il Dottore, the ringleader of the crimes.