John Anderssen has a readheaded wife who claims to a witch and proves it to him one night by disappearing most effectively.
The gimmick for this one came to Asimov in a dream, and in the afterword he wishes aloud that his dreams helped him a bit more along those lines by coming up with the puzzles for him to put in his stories for him. This reader wishes the same; the story here is far, far better and more effective than the average Black Widower story with a believable and interesting resolution.
My wife, by the way, is a redhead. I just thought I’d mention that.