By Brian Hayles And Terrance Dicks
It is the 21st century and Earth is totally dependant on T-Mat, a revolutionary form of instant travel. When the system breaks down the Doctor and friends make a hazardous journey to the moon only to find it has fallen into the hands of the Ice Warriors who plan to invade the 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 the dying world?