First aired (in inner space) on June 13, 1977, and written by Victoria Dann (who must have somehow been related to Sam Dann).

Taking place entirely on Earth, this episode stars noteable TV actress Phyllis Newman in the title role as a scientist named Margo Gordon, whom after returning from a trip in space is haunted by an unseen female voice of a woman who is the sole survivor whose planet was destroyed when their sun exploded. She made the trip by inhabiting Margo's body. This serious story is very different for Ms. Newman, who usually did light work and comedy.

It's actually better than William Shatner's experiences with a puppet-like alien in the 1964 Outer Limits episode "Cold Hands, Warm Heart", whose astronaut character was haunted by the creature while in deep space, only to make his body temperature go haywire after returning to Earth. Of course...that alien didn't follow Bill back to our world!