From BBC Video! The Doctor (Tom Baker), Sarah and Harry return to Earth in response to the Brigadier's summons. UNIT are investigating a series of attacks on North Sea oil rigs and have set up a temporary HQ controlled by a group of aliens called Zygons whose spaceship lies at the bottom of Loch Ness. The Zygons plan to take over the Earth as a subsitute for their own planet, which has been devestated by solar flares. They are using their shape-shifting abilities to take on the identities of locals whose inert bodes are held aboard their ship.
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