The Cat O' Nine Tails/Il Gatto a Nove Code (1971)

Former journalist Franco Arno is a retired blind man who likes crosswords and lives with his orphan niece Lori near the Terzi Institute. While walking with Lori on the street, he overhears a strange conversation of two men in a car parked in front of the institute and he asks Lori to watch their faces. The same night, there is a break in at the institute with an attempt of heist. The next morning, researcher Dr. Calabresi dies in the train station and the police believe that it was an accident. However, Lori recognizes the picture of the scientist in the newspaper as one of the men in the car. Franco contacts the snoopy reporter Carlo Giordano and asks him to blow up the picture and examine the details. The photographer discovers that Dr. Calabresi was pushed off from the platform but he is also killed and the photograph vanishes. After their preliminary investigation, they find that the scientists are researching a revolutionary drug and a genetic experiment of XYY chromosomes associated to delinquency for the government and they conclude that there are nine leads to be followed: each of the five assistants of the institute (Dr. Calabresi; Dr. Esson; Dr. Mobelli; Dr. Casoni; and the gay Dr. Braun); the stepdaughter of Prof. Fulvio Terzi, Anna Terzi; the fiancée of Dr. Calabresi, Bianca Merusi; the missing photograph; and the robbery of the institute.

IMDb: https://www.imdb.com/title/tt0065761