Casting Guest stars included
Tab Hunter,
Helen Hayes,
Jason Robards,
Patricia Neal,
William Windom,
Gena Rowlands,
Carolyn Jones,
Melvyn Douglas,
Stella Stevens,
Tyne Daly,
David Soul,
Karen Black and
Jodie Foster.
D.C. Fontana scripted the episode "Earth, Air, Fire and Water", based on a story by herself and
Harlan Ellison. Both writers had worked on
Star Trek, the former extensively.
Renaming Beginning with "Death's Head", the series' fourteenth episode, which aired on January 5, 1973, the series was renamed
Circle of Fear. {{cite book {{cite book The change was necessary, according to executive producer William Castle, because of low ratings. He attributed the title change to the head of the production company,
Screen Gems. Additionally, Cabot was dropped as the presenter.{{cite news The opening title graphics and theme music were also changed. This reworked version lasted nine further episodes. {{cite book ==Episodes==