The title credits include special participation by Basil Rathbone and Boris Karloff. Both men were deceased, having died in the late 60s. However, they appear in clips from real films they acted in with Vincent Price: Rathbone in Tales of Terror and Karloff in The Raven.
The title has very little to do with the film. There is a brief scene in a mental institution; and we learn in some expository dialogue that the main character spent time there. Otherwise, the "madhouse" of the title is irrelevant.
The trivia item below may give away important plot points.
The finale involves one character applying make-up to pass for another. This premise depends upon such unlikely 'transformation' having at least a glimmer of credibility. Poor quality prints spoil this illusion and thus the very ending itself. There is a high-quality (anamorphic transfer) DVD available which gives the audience the benefit of the intended effect.