According to an interview in the book The Twilight Zone Companion, writer Richard Matheson based this story on a real-life occurrence involving his own daughter. Said Matheson, "she cried out one night and I went to where she was and couldn't find her anywhere. I couldn't find her on the bed, I couldn't find her on the ground. She had fallen off and rolled all the way under the bed against the wall. At first, even when I felt under the bed, I couldn't reach her. It was bizarre, and that's where I got the idea."
The only TZ episode for the score-writer to be credited before the director (for the vitality of the episode's music).
The street scene at the end is a staple used in numerous other TZ episodes.