Great Casting

Laird Cregar was perfect for this role, I can't think of anyone in Hollywood at the time who could bring the same level of menace balanced with awkwardness (you just know this guy was bullied in grade school). Merle Oberon is great as the beautiful Kitty; I like that she isn't the typical screamer, rather she handles herself well once Cregar reveals himself as a killer. You can see her thinking about how to get out of the situation without falling apart.

Also Sara Allgood put forth a great performance as the landlady who is suspicious but doesn't want to think the worst of her well-paying boarder.