The HQ is destroyed by the web and everyone is captured by Yetis. The traitor is revealed and all seems lost as the Doctor submits himself to the Great Intelligence's mind drain. 

The Daleks force the Exillons to work as slave labour to mine the life-saving parrinium. The Doctor and Bellal brave the puzzles and traps of the Exxilon city.

A two-part story by Glen McCoy
Starring Colin Baker
On Karfel the Borad rules but all is far from OK.
CEEFAX SUBTITLES

Francesca Miller played a younger version of Andrea Yates in Whatever Happened to Sarah Jane?.

Mark Straker played a Trooper in the 1983 Doctor Who television series Earthshock.

Also worked on EastEnders, Law & Order: UK, Doctors, Ashes to Ashes, Spooks, Judge John Deed, Batman Begins, Footballers' Wives, Life Begins, The Bill, Murphy's Law, Shiner, Randall & Hopkirk (Deceased), Casualty, The Lakes, Dangerfield, The Life of Confucius, Melissa, Testament: The Bible in Animation, Hotel Hilbert, Lovejoy, Birds of a Feather

Chris Clough (born in Harrogate, Yorkshire, England) is an English director and producer of television.

Clough studied English literature at Leeds University. He went there because they had a television studio available for the students. He used the material he created there to apply for jobs and he got a job as a researcher at Granada Television. He then started directing. In 1982 he went freelance and in that decade he directed episodes of TV-series such as Brookside and EastEnders.

While working on EastEnders, Clough got to know one of the assistant directors, Gary Downie, who had also worked on Doctor Who. He got an interview with Doctor Who producer John Nathan-Turner and he ended up directing six serials of the series � Terror of the Vervoids, The Ultimate Foe, Delta and the Bannermen, Dragonfire, Silver Nemesis, and The Happiness Patrol.

In the 1990s, Clough directed several episodes of The Bill and he also started producing the show in the latter half of the decade. He then went on to produce several other series, including Ballykissangel, Black Cab, and The Ghost Squad. He currently produces the E4 Teen Drama Skins and Channel 4 drama Sirens.

Biography from the Wikipedia article, licensed under CC-BY-SA 

Tom Adams is an English actor with roles in horror and mystery films, and several TV shows.

He starred as Charles Vine in Licensed to Kill (aka The Second Best Secret Agent in the Whole Wide World, 1965) and the sequels Where the Bullets Fly (1966) and Somebody's Stolen Our Russian Spy (1967).

His television credits include General Hospital (1972); The Onedin Line as Daniel Fogarty (1977-1979) and Emmerdale Farm as Malcolm Bates (1987).

For many years in the 1980s and '90s he was the face of furniture stores DFS. 

Peter Hill played the manager in the 1972 Doctor Who story Day of the Daleks.

Also worked on Crossroads, The Professionals, Dick Turpin, Rings on Their Fingers, In Loving Memory, The Fall and Rise of Reginald Perrin, Target, The Finishing Line, The Cedar Tree, Big Boy Now!, Thriller, Rock Follies, Comedy Premiere, Dixon of Dock Green, A Little Bit of Wisdom, Centre Play, General Hospital, The Hole in the Wall, Softly Softly: Task Force

Eddie Powell  played Thompson in Daleks' Invasion Earth 2150 A.D..

Keith Pyott  was a British actor.

He transferred from stage to screen and was a regular face in drama in the early days of television, appearing in The Prisoner, Out of the Unknown, The Avengers and the Doctor Who storyThe Aztecs.

He also appeared in over twenty feature films, including Orson Welles' Chimes at Midnight (1965).

Working his way up the ranks in the BBC, Jeremy Silberston became a Production Manager in 1982 and worked on a number of shows as well as Doctor Who, including Smiley's People, Lovejoy and Bergerac. As a director he worked on shows like The House of Elliott, Coasting and The Bill

A good friend of Anthony Horowitz, the two of them developed both Midsomer Murders and Foyle's War, with Silberston directing a number of their episodes.

Terry Nation was a Welsh novelist and screenwriter best known for creating the Daleks for Doctor Who and the BBC series Survivors and Blake's 7.

Nation was born in Cardiff in Wales. He initially worked in comedy working for Associated London Scripts alongside Johnny Speight and John Junkin. He wrote for scores of British comedians including Terry Scott, Eric Sykes, Harry Worth and Frankie Howerd. His big break came in 1962 when he was commissioned to write material for the comedian Tony Hancock, initially for Hancock's new ATV television series and later for his stage show.

Nation accompanied Hancock as his chief screenwriter on tour in 1963, but Hancock continually fell back onto his old material and failed to use Nation's scripts. The two quarrelled and Nation was fired. At the same time nation was approached by Doctor Who script Editor David Whitaker to contribute to the new science-fiction series. Whitaker had been impressed with a script Nation had written for the science fiction anthology series Out of this World for ABC. Nation took up the offer, writing the second Doctor Who serial - The Daleks  which saw the introduction of the creatures that would become the show's most popular monsters

Nation went on to contribute several further scripts to Doctor Who. Various Dalek spin-off material appeared, including a comic strip in TV Century 21 and annuals. 

He also contributed episodes to such shows as The Avengers, The Baron, The Persuaders!, The Champions, Department S, and The Saint. In the late 1960s Nation attempted to launch the Daleks as a series in their own right in the United States, but this was not successful.

In the early 1970s the BBC commissioned  him to create a new science fiction drama series. Survivors was a post-apocalyptic tale of the few remaining humans, the population having been devastated by a plague. The show was well received, but Nation's vision for it conflicted with that of producer Terence Dudley and the other two seasons were produced without his involvement. 

His next BBC creation, Blake's 7, was more successful. The show told the story of a group of criminals and political prisoners on the run from the sinister Federation in a stolen alien space ship of unknown origins. It ran for four seasons from 1978 to 1981. Nation wrote the entire first season of the series. His input decreased over the run, the overall direction eventually being controlled by script editor Chris Boucher, with Nation not writing at all for the fourth and final season. 

In 1980 Nation moved to Los Angeles, California where he developed programme ideas and worked for various studios. Little of his work in this time was as successful as his original period in the United Kingdom. He contributed to the American TV series MacGyver, in addition to television series such as A Masterpiece of Murder and A Fine Romance.

Nation died from emphysema in Los Angeles on 9 March 1997.