After the retirement dinner for Tony Pacelli's 21 years of service to the NYPD

He returns to his Manhattan apartment to find a letter from his beloved aunt, Zia Erna. She asks him to solve the many thefts at her hotel (Il Bel Fior) located in the Val D'Adige region of North Italy.

While staying at the hotel

The prestigious Signora Louisa de' Medici is murdered and her da Vinci masterpiece is missing. The carabiniere Ispettore Portari, with the help of Tony Pacelli and the Firenze Polizia, form an investigative team which are left to solve the masterpiece theft and the felony murder of Signora de' Medici.