'Terror of the Zygons' (4 Parts) Story Code '4F' by Robert Banks Stewart

Returning to Earth in answer to the Brigadier's summons, the Doctor, Sarah and Harry arrive in the Scottish village of Tullock. UNIT is investigating a series of attacks on North Sea oilrigs in the area, and have set up their headquarters in the village. The Caber, servant of the Duke of Forgil, shoots Harry, who is taken to hospital to recover. While visiting him there, the Doctor and Sarah are almost killed by Sister Lamont, who then escapes into the woods. Harry is kidnapped, replaced by a murderous duplicate, and taken prisoner in a strange bio-organic spaceship which is resting on the bed of Loch Ness. The Doctor and Sarah visit the Duke at his mansion, and find a secret passage leading to the crashed spaceship. The Doctor discovers that the Skarasen, a gigantic cyborg living in Loch Ness, is the cause of the attacks. The creature is being controlled by the Zygons, aliens who are planning to take over the earth, as their own planet has been devastated by solar flares. The Zygons have used their shape-shifting abilities to take on the identities of the locals, whose inert bodies are being held aboard their ship. The Doctor releases the prisoners, and sets their ship to self-destruct. As the craft explodes, they realise that Broton, the Zygon leader disguised as the Duke of Forgill, has escaped and travelled to London. Broton plans to destroy a world energy conference using the Skarasen, which is now swimming along the Thames. Broton is killed by UNIT troops, and the Doctor frees the Skarasen from the Zygons' influence, leaving it to make its way back to Loch Ness. Harry decides to stay with UNIT.

Tom Baker (Doctor Who), Elisabeth Sladen (Sarah Jane Smith), Ian Marter (Harry Sullivan), John Woodnutt (Duke of Forgill), Nicholas Courtney (Brigadier Lethbridge-Stewart), John Levene (RSM Benton), Lillias Walker (Sister Lamont), Robert Russell (The Caber), Angus Lennie (Angus), Tony Sibbald (Huckle), Hugh Martin (Munro), Bruce Wightman (Radio Operator); Keith Ashley, Ronald Gough (Zygons); Bernard G. High (Corporal), Peter Symonds (Soldier)

Produced by Philip Hinchcliffe
Directed by Douglas Camfield

TX:
Part 1 - 30th August, 1975 @ 5.45pm - 6.10pm
Part 2 - 6th September, 1975 @ 5.45pm - 6.10pm
Part 3 - 13th September, 1975 @ 5.45pm - 6.10pm
Part 4 - 20th September, 1975 @ 5.20pm - 5.45pm

Notes:
*Featuring the Fourth Doctor, Sarah, Harry, the Brigadier and UNIT

*First appearance of the Zygons

*Working titles: 'The Loch Ness Monster', The Secret of Loch Ness', 'Doctor Who and the Zygons' and 'The Loch Ness Terror' (the last was a BBC Publicity error)