The last 20 minutes are so amazing. The suspense!
Matte paintings and sexual tension straight from the start are amazing and everything is so masterfully done, but enough can't be said about the last 20 minutes or so.
It goes way beyond what Hitchcock were doing at the time (or ever did). It almost reminds me of The Exorcist or some De Palma films that came out many decades later. Amazing film. One of the greatest films ever.