R.R.R.R. (1965)
Hitchcock approached Italian comedy-thriller writers Agenore Incrocci and Furio Scarpelli (Age & Scarpelli), writers of Big Deal on Madonna Street, to write a screenplay around an original idea Hitchcock had carried in his head since the late 1930s. A New York City hotel run by an Italian immigrant and his family who, unknown to him, are using the hotel as cover for crimes, including the theft of a valuable coin from a guest of the hotel. (R.R.R.R. is the highest value of coin.)
The Italian screenwriters struggled with the story, and were not helped by the language barrier. Universal Studios were not keen on the idea and persuaded Hitchcock to move on to something else.
Read more about this topic: List Of Unproduced Hitchcock Projects