Alfred Hitchcock based the killer on Jack The Ripper, and
because the Ripper was never caught, I don't think Hitchcock would
have revealed his serial killer either.
Related Q&A：
Who was the killer in the movie the lodger？-Well, let me tell ya. In \The Lodger,\ the identity of the killer is a bit of a twist. It turns out to be a character who seemed quite innocent and unassuming at first. But as the story progresses, you start to notice some strange behaviors and clues that point to them. Oh my goodness, it's one of those moments that really keeps you on the edge of your seat. It's not someone you would expect, which makes the whole plot even more exciting and surprising!
