About the Doctor Who Terror of the Zygons DVD

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.