It is the 21st Century and Earth is totally dependent on T-Mat, a revolutionary form of instant travel. When the system breaks down The Doctor and friends make a hazardous journey to the relay station on the moon only to find that it has fallen into the hands of the Ice Warriors who plan to invade Earth.
Using T-Mat, the Ice Warriors transport seed pods to Earth which burst, disgorging a deadly Martian fungus. This spreads rapidly, extracting vital oxygen from the atmosphere. Can The Doctor outwit the evil Ice Warriors and destroy the fungus in time to save a dying world?
NOTES
The working title of this story was The Lords of the Red Planet.
Although Brian Hayles is solely credits as the story’s author, series script or Terrance Dicks rewrote Episodes 3 through 6 of the script, partially as he considered Hayles’s original ending lackluster and unworkable but also because originally Jamie McCrimmon was to have been replaced by a new companion called Nik by this story, but then actor Frazer Hines postponed his departure. Dicks was co-credits on the sleeve of the release for his writing duties on the serial.
Patrick Troughton does not appear in Episode 4 as he was on holiday when it was being recorded. A double stands in for him in some shots where The Doctor is seen unconscious on the floor.
Model sequences of the Earth and the Moon are used as a backdrop to the story title, writer and episode number captions at the start of each episode.
A prop previously seen as the TARDIS astral map, as introduced in season two’s The Web Planet, appears as one of the exhibits in Eldred’s museum of space flight.
Zoe’s leather outfit was primrose yellow in colour. Actress Wendy Padbury was allowed to keep it as an addition to her own wardrobe after recording of the story was completed.
