It is well known that directors have lots of movie ideas, scribbles or sometimes unfinished projects, mostly because of production companies change their minds and interests to the movie.
After the ominous effects of "Marnie" (personally I like it) and "Tony Curtain" (personally, not my favorite Hitchcock either), Hitchcock apparently wanted to try a different style to shake off the suspenses of the time. Hitchcock is famous to be touching to the taboo subjects of the time (such as in Psycho, Topaz...). This time, the movie's main character was a serial-killer and the story was told from his perspective. It was meant to be a glimpse to the story of a killer, a rapist psychopath. Also, the scenes were intended to have more nudity and blood.
The movie's name is referred to as "Kaleidoscope" and intended to be shot with a handheld camera. The footages of the film are shot in 1967. However, horrified by the extreme nudity and explicitness of the movie, this time the production company turned down the project. We can only imagine what it would look like by reading about its script and watching other Hitchcocks, especially "Frenzy". Later, Kaleidoscope inspired his next movie "Frenzy" and some of the ideas are used there.