Cat o' Nine Tails (1971) Dario Argento

Franco Arno is a blind man that lives with his young niece and makes a living writing crossword puzzles. One night, while walking on the street, he overhears a weird conversation between two man sitting in a car parked in front of a medical institute where genetic experiments are performed. The same night someone breaks in the institute and knocks out a guard. Arno decides to investigate with the help of reporter Carlo Giordani.