them to Lunarville 7. While retiring for the night, the officers find that their accommodation has been bugged. Rising early, Scarlet attempts to request a Moonmobile from SID but discovers that the Controller has re-programmed the computer to accept only his commands. Scarlet also learns that the Controller has declared a state of emergency and ordered the evacuation of Lunarville 7. Scarlet switches recognition discs with the sleeping Controller to trick SID into giving him, Blue and Green a Moonmobile. Travelling to the Humboldt Sea, the officers discover a Mysteron installation under construction in a crater numbered "101". Returning to Lunarville 7, Scarlet, Blue and Green confront the Controller and Orson, who appear to be Mysteron reconstructions. Scarlet, still wearing the Controller's disc, instructs SID to prepare an Earth-bound shuttle for immediate departure. When SID rejects the Controller's order to lock down the colony, the Controller produces a handgun and repeatedly shoots SID, causing an explosion that obliterates the control room. Scarlet, Blue and Green blast off in the shuttle before further explosions destroy the whole colony. Production The episode was filmed on Century 21 Studios' Stage 4. In his speech at the beginning of the episode, the Lunar Controller states that the Moon is home to approximately 4,000 people. In Barwick's original script, the character was then to have discussed the Moon's self-reliance in greater detail, declaring, for example: "We were all born on Earth, but I see a future where men will be born, spend their lives and die on the Moon." However, these lines were cut from the finished episode. The electronic voice of SID was provided by supporting voice actor Martin King, who spoke his lines into a vocoder supplied by Standard Telecommunication Laboratories of Harlow. The episode's closing titles credit STL for "electronic collaboration". The miniature model of Lunarville 7 was built partly out of colanders and mixing bowls. Some elements of the puppet set design were recycled from Century 21's previous series, Thunderbirds: the Moonmobile cockpit incorporated sections of the interior of Thunderbird 4 and the Lunar Controller's desk was a modified form of the Glenn Field controller's desk from the film Thunderbirds Are Go (1966). The Moon shuttle cockpit was a red-dress of the Martian Exploration Vehicle interior first seen in Thunderbirds Are Go and again in "The Mysterons". The Lunarville Moonmobiles influenced the look of the SHADO Moonmobiles in Century 21's live-action