This episode required a 16-minute overrun, brought about by a variety of flubbed lines, missed cues, equipment problems, and troubles with the Zarbi costumes, one of which broke and had to be repaired.
This was the first of two William Hartnell serials that Arne Gordon has roles in. The other was Flight Through Eternity (1965).
This was the first of two William Hartnell serials that Roslyn De Winter has roles in. The other was Journey Into Terror (1965).
This episode was watched by 12.5 million viewers on its original transmission.