This was filmed as a pilot for a new Joseph Stefano series. When it didn't sell, it was partially re-shot (adding fantasy elements) and shown as an episode of his sci-fi anthology series The Outer Limits (1963) entitled The Forms of Things Unknown (1964). Both versions exist.
Dominic Frontiere's score was used in subsequent television series, most notably the fourth season of The Fugitive as well as The Invaders, whose opening theme is the same as in The Unknown.