The only reason I wanted to watch this is for the connection to _Kill Bill_ (2003). This begins as a slow, psychological thriller, and I had to stop it halfway through, out of boredom. However, it does pick up after that, and becomes more of a horror movie. With this being made in the late 1960s, it didn't have the luxury of a by-the-numbers slasher template. Slashers didn't exist then. The closest examples would have been _Psycho_ (1960), and _Peeping Tom_ (1960); hell, even _The Collector_ (1965) probably had an influence. All that is to say, the movie is not very impressive. It's boring, the story is weak, it tries to squeeze in some depth about the psychological explanation for our antagonist. With just a few tweaks to the story, this one would be a classic. What really saves the movie is Hayley Mills. She is fantastic. The whole cast is good, actually, but she is the clear standout. I can't recommend this one, but if you like '60s horror/thrillers, give it a watch.