This episode was one of
John Erman's earliest jobs as a director and depicts Earth soldiers who have been captured and are being tormented by aliens on a mostly barren set, consisting of a few rock-like props and doorways. It bears many striking similarities to
The Empath (1968), also directed by Erman, in which Kirk, Spock, McCoy and the titular empath Gem, played by
Kathryn Hays, spend the majority of their screentime on a mostly bare set consisting of a few props and dark curtains, also being tormented by aliens.
Willard Sage appeared in both episodes, playing the Chief of Staff in this episode and Thann, one of the alien tormentors, in that episode.