A number of plot changes were made to this episode during the transition from script to screen:
- The original script makes clear that there is no traitor (and the Mysterons' only involvement has been to cause unrest within Spectrum), that the valve failed due to the extremely high temperatures in the Outback, and that the fire in Scarlet and Blue's quarters was an accident.
- A shot of Machin lurking outside the room before the fire breaks out was filmed but ultimately cut, leaving only a brief glimpse of a departing figure.
- Cut dialogue indicates that Johnson is Major Stone's nephew, which explains why Stone does not suspect him of being the traitor.