The Girl Who Knew Too Much (1963)

American friends Nora (Leticia Roman) and Edith (Chana Coubert) are on vacation in Rome. But on their first night in Italy, Edith mysteriously dies — and Nora witnesses a murder on the Piazza di Spagna. The only person who will take Nora seriously is a doctor (John Saxon), who tells her the killing she witnessed was committed 10 years ago by the Alphabet Murderer. Mario Bava directs this stylish homage to Alfred Hitchcock.