The scene where Henry ("Manny") Fonda is taken to prison was filmed in a real prison. As he is led to his cell , you can hear one of the inmates yell out "What'd they get ya for, Henry??", and a bunch of other prisoners laughing.
On the DVD, the running commentary revealed that when the crew went to film the scenes at the country hotel, Alfred Hitchcock stayed in his limo due to the cold outside and decided to move the production to Hollywood to complete the film.
According to the book "It's Only a Movie", Alfred Hitchcock asked John Michael Hayes to work on the treatment and screenplay of this film for no salary but for a percentage of the profits. Hayes declined, and their four-picture relationship ended.
In the opening scene, it shows Manny (Henry Fonda) playing his bass viol. Seated at the piano, next to him is the pianist/conductor who tags the final note played. This is in reality Betnard Herrmann, the composer and conductor for many Hitchcock movies and many other Hollywood films of that era.