Late in the filming of the second season, Richard Basehart fell ill during the filming of the episode "The Monster's Web" and was unable to complete that episode and work in the next two. "The Monster's Web" was rewritten to minimize the part of his character, Adm. Nelson (knocked out of action in the first act), with a stand-in used for many shots with the face hidden and lines dubbed.
This episode takes place in the 1970s.