27th September – 18th October 1980
He sees the threads that join the Universe together, and mends them when they break.
Zastor on the Doctor, episode 1
The two governing houses on Tigella are squabbling again. The science-based Savants and the religion-centred Deons cannot agree on how to rectify fluctuating power levels from their underground city’s sole power source, a mysterious stone, the Dodecahedron. The leader of their two houses, Zastor (Edward Underdown) decides to send for his old acquaintance, the Doctor.
Meanwhile, on Tigella’s long-believed dead twin planet, Zolpha-Thura, a gleaming laboratory rises up from beneath the desert sands, greeting the arrival of a gang of space mercenaries, the Gaztaks led by General Grugger (Bill Fraser). The laboratory’s sole occupant is Meglos, the last survivor of the shape-changing Zolpha-Thurans, who has preserved himself for many years in the form of a cactus. Using his advanced technology, Meglos has contacted and commissioned Grugger to capture an earthling and bring him here so he can occupy a human body and become mobile again. With help from his Gaztak mercenaries, Meglos plans to raid Tigella and capture the Dodecahedron in the first stage of a plan to restore Zolpha-Thura’s pre-eminence in the galaxy.
Meglos manages to mould his new humanoid body into a form identical to the Doctor. Once on Tigella he persuades Zastor to leave him alone in the power room, and then steals the Dodecahedron. When the real Doctor lands, he is mistaken for the person who stole the great stone.
Meglos slips away in the ensuing confusion, leaving the Doctor to face trial and execution. After unwittingly helping Meglos escape the planet, Romana enlists help from a Savant, Caris (Collette Gleeson) to storm the Power Room and explain the situation – and not before time, as they find the Doctor spread-eagled on a slab and about to be crushed to death by a sacrificial stone.
The Doctor leads the Deons and the Savants to Zolpha-Thura, just as Meglos is about to use the power of the Dodecahedron to destroy Tigella. But, by switching the settings on Meglos’s device, the Doctor turns the tables and instead Zolpha-Thura is the planet that is destroyed.
The Tigellans can now start reclaiming the surface of their planet, no longer able to rely on the Dodecahedron for energy.
Video © BBC