This episode was the first and final time since the pilot that a leading officer of Spectrum would be killed and reconstructed by the Mysterons. However, as producers did not want to kill off one of the regular officers that viewers would by now be used to, they introduced Captain Indigo as an extra captain in order to achieve this. Like Captain Brown in the pilot, this would mark Captain Indigo's one and only appearance in a story.
Due to the assigned Spectrum officers being undercover and out of uniform, Captain Indigo (in his only appearance) was never seen in his color coded Spectrum uniform. Captain Indigo was also - along with Captain Blue and Lieutenant Green - one of only three officers to be color coded with an actual color of the visible color spectrum as seen on their emblems.