The Girl Who Knew Too Much is a 1963 Italian giallo film directed by Mario Bava, starring John Saxon as Dr. Marcello Bassi and Letícia Román as Nora Davis. The plot revolves around a young American woman named Nora, who travels to Rome and witnesses a murder. The police and Dr. Bassi do not believe her, since a corpse has not been found. Several more killings follow, tied to a decade-long string of murder victims chosen in alphabetical order.