Neat Little Thriller
This is one of Hammer's best 1960s efforts in the 'thriller' category - a tight script by Jimmy Sangster, crisp B&W photography, good music, creepy mise-en-scene, and excellent performances from Strasberg, Lee, Lewis and the ever-lovely Ann Todd.
This one's worth a re-watch every few years, and knowing how it all comes out doesn't make revisiting it any less interesting.
"Remind me to tell you about the time I looked into the heart of an artichoke."