At the end of the twenty-first century, a teleportation technology called "T-Mat" has replaced all traditional forms of transport, allowing people and objects to travel instantly anywhere on Earth. Manned space exploration has ceased due to the ease of life on Earth. The Doctor, Jamie McCrimmon and Zoe Herriot arrive in a museum on Earth run by Professor Daniel Eldred dedicated to the obsolete technology of rockets. However, something goes amiss at the T-Mat vital relay station on the Moon and the system breaks down. With communications out, and no way to reach the Moon without T-Mat, those responsible for the system, Commander Radnor and his assistant Gia Kelly, turn to Professor Eldred to help. He has been privately building a rocket in hopes of re-igniting interest in space travel. The Doctor and his companions volunteer to crew the rocket. The Doctor also comments that the TARDIS is not suitable for short range use after Zoe informs Jamie that the TARDIS would most likely overshoot by a couple of million years. The relay station on the Moon has been invaded by Ice Warriors, a militant Martian race, who plan to use it as a staging point for an invasion of Earth. The technicians attempt to fight the invaders but several are killed, while Phipps goes into hiding and Fewsham is pressed into assisting the invaders. Fewsham repairs the T-Mat link on receive mode and Miss Kelly beams through to start repairing the T-Mat system. When the Doctor and his companions arrive on the Moon they make contact with Phipps, who is hiding in the moonbase. The Doctor accidentally reveals himself to the Ice Warriors and their leader Commander Slaar. The Ice Warriors have a deadly plan: they have seeds, which they send to various parts of Earth using T-mat, of a fungus that will multiply and suck all the oxygen from the surrounding atmosphere, making it more comfortable for the Martians but uninhabitable for humans. Once the full T-Mat relay is repaired, one seed is sent to Earth Control and explodes, killing a technician and alerting Radnor and Eldred of the danger. The seed soon creates foam, which multiplies its effects and imperils more and more people. Other T-Mat terminals across the world receive more seeds. The Ice Warriors also use T-Mat to dispatch a small advance force to seize Earth's weather control systems in London and ensure good conditions for the growth of the fungus. On the Moon Miss Kelly and Phipps work with Zoe and Jamie to stage diversions and attacks against the Ice Warriors. During their main assault to free the Doctor, Phipps is killed. The Ice Warriors have now retreated to their spacecraft to plan the next stage of their invasion, leaving an opportunity for most of the captives to flee. Fewsham, however, remains behind, seemingly fearing an enquiry into his actions if he returns to Earth. In T-Mat control on Earth, the Doctor works out that the seed pods can be defeated using water. This explains where the Ice Warrior beamed to Earth has gone, and the Doctor tracks him down to the weather control system, where the alien has been stationed to prevent any rain fall that would be deadly to the pods. The Doctor and his allies recapture the weather control system and summon rain, destroying the fungus, which is used to the dry conditions on Mars. Fewsham has meanwhile delivered a crushing blow to the Ice Warriors. He dupes Slaar into revealing in a live link with Earth that the main invasion force is following a homing signal to the Moon, for which he is killed. But at least the Doctor now knows the full extent of the Ice Warrior plans. He returns to the moonbase by T-mat to set a new signal for the Martian fleet from there. The Doctor confronts Slaar while substituting the alternative signal. This draws the Martian fleet away and lures it into the Sun. Slaar moves to kill the Doctor in revenge but the arrival of Jamie in a T-Mat cubicle causes chaos, and Slaar is killed in one of the sonic beams of the last of his warriors. Jamie then kills the surviving Martian and the invasion is over. The Doctor and Jamie return to Earth and then make their goodbyes before departing in the TARDIS with Zoe.
Production
Although Brian Hayles is solely credited as the story's author, series script editor Terrance Dicks rewrote Episodes 3 to 6 of the script. This was partly because he considered Hayles's original ending lacklustre and unworkable, but also because originally Jamie McCrimmon was to have been replaced by a new companion called Nik by this story; actor Frazer Hines postponed his departure, however. Dicks was co-credited on the sleeve of the VHS 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.
Cast notes
This story is the first story to feature Alan Bennion in the role of an Ice Lord, this one named Slaar. Bennion would return as the Ice Lords Izlyr in The Curse of Peladon and Azaxyr in The Monster of Peladon. Sonny Caldinez, who played Slaar's second in command, is the only actor to appear as an Ice Warrior in all four televised Doctor Who stories in the classic series to feature the Ice Warriors. Caldinez also appeared as Kemel in The Evil of the Daleks. Ronald Leigh-Hunt played Commander Radnor in this story. Leigh-Hunt would play Commander Stevenson in Revenge of the Cybermen. Harry Towb later played McDermott in Terror of the Autons. Christopher Coll would later play Stubbs in The Mutants. Steve Peters, who played an Ice Warrior, was billed simply as "Alien" in the Radio Times listing for episode one, so as not to spoil the surprise of the Ice Warriors' appearance.
Commercial releases
In print
A novelisation of this serial, written by Dicks, was published by Target Books in July 1986.
Home media
This story was released on VHS and Betamax in 1985 in an omnibus format. In February 2003, an unedited remastered, VidFIREd version was released on Region 1 and Region 2 DVD. The story was chosen to represent the Patrick Troughton era as part of the Doctor Who 40th Anniversary releases. A special edition Region 1 and 2 DVD with expanded special features and improved picture quality was released along with similarly expanded special editions of the Carnival of Monsters and Resurrection of the Daleks as part of the Revisitations 2 DVD boxed set on 28 March 2011 exclusively in the UK.
