The TARDIS is attacked in space by a mysterious web-like substance, and is forced to land, whereby it materialises at a London Underground station. The rail tunnels have also been overrun by the web substance, and also by robotic Yeti.
Professor Travers, whom the Doctor and Victoria first met in the Himalayas, has accidentally caused one of the Yeti to become activated, paving the way for another invasion attempt by the Great Intelligence.
The Doctor works with the military, led initially by Captain Knight, and later Colonel Lethbridge-Stewart. However, Staff Sergeant Arnold's mind has come under the control of the Great Intelligence, and this hampers Lethbridge-Stewart's investigations.
The Great Intelligence has created a device that will allow it to steal the mind of the Doctor. The Doctor manages to reverse the polarity and can use the device to feed off the Great Intelligence. He almost succeeds, until he is rescued, and the Great Intelligence is repelled into space.
Regular castJamie McCrimmon: Frazer Hines; Victoria Waterfield: Deborah Watling;
Guest castProfessor Edward Travers: Jack Watling; Anne Travers: Tina Packer; Staff Sergeant Arnold: Jack Woolgar; Captain Knight: Ralph Watson (1-4); Corporal Lane: Rod Beacham; Corporal Blake: Richardson Morgan (1-4); Harold Chorley: Jon Rollason (1-2,6); Craftsman Weams: Stephen Whittaker; Yeti: Roger Jacombs (6), Jeremy King (3), John Levene (1-2,4-6), John Lord (1-2,4,6), Gordon Stothard (1-2,4), Colin Warman (1); Julius Silverstein: Frederick Shecker (1); Soldiers: Bernard G High (1), Joseph O'Connell (2); Driver Evans: Derek Pollitt (2-6); Colonel Lethbridge-Stewart: Nicholas Courtney;
Uncredited cast: Dead Newpaper Seller: Bert Sims (1); Soldiers: Peter Adams, Maurice Brooks, Tim Condren, David Hacquet, James Jordan, Philip Ryan; Extras: Douglas Kirk, Derek Martin, Terry Walsh;
|BBC 1||192||Episode 1||Sat 3 February 1968||5:25 pm - 5:50 pm||7.2M||82nd|
|BBC 1||193||Episode 2||Sat 10 February 1968||5:15 pm - 5:40 pm||6.8M||80th|
|BBC 1||194||Episode 3||Sat 17 February 1968||5:25 pm - 5:50 pm||7.0M||71st|
|BBC 1||195||Episode 4||Sat 24 February 1968||5:25 pm - 5:50 pm||8.4M||52nd|
|BBC 1||196||Episode 5||Sat 2 March 1968||5:25 pm - 5:50 pm||8.0M||48th|
|BBC 1||197||Episode 6||Sat 9 March 1968||5:25 pm - 5:50 pm||8.3M||36th|
Repeats (on the BBC)
Greenwich Footway Tunnel, London; Old Covent Garden, London;
Ealing Television Film Studios; Lime Grove Studio D;
Bloopers and mistakes
The Yeti changes shape in the museum scene.
When talking about 'underground trains', the Doctor says that this is 'a little after your time, I think, Victoria'. The underground line between Farringdon Street and Edgeware Road opened in 1863 but Victoria comes from 1866.
Notes and trivia
The end credits are scrolled over footage of multiplying cells.
This programme has no other working titles, or they have not been yet been entered.