1 September 1979
Tim Barlow (Tyssan), Peter Straker (Commander Sharrel), Suzanne Danielle (Agella), Tony Osoba (Lan), Mike Mungarvan, Cy Town (Dalek Operators), Roy Skelton (Dalek Voices), David Gooderson (Davros) [2-4], Penny Casdagli (Jall) [2, 4], David Yip (Veldan) [2, 4], Cassandra (Movellan Guard) 
|Written by||Terry Nation|
|Directed by||Ken Grieve|
|Produced by||Graham Williams|
Accompanied by the newly regenerated Romana, The Doctor lands on a mystery planet intrigued by the evidence of drilling taking place there, deep underground. The discoveries he makes are chilling. For the planet is Skaro and the Daleks are in charge of the operation. But just what are his old enemies searching for? And why?
Perhaps the answers lie with the Movellans, a beautiful humanoid race led by Commander Sharrel. They are waging a war of their own with the Daleks and the situation is now stalemate. Should The Doctor tip the balance of power to aid the Daleks’ ultimate destruction? Or are their intentions no less sinister than the Daleks’ themselves? Suddenly The Doctor finds himself enmeshed in a deadly battle which could result in the destruction of the universe itself as, once more, he summons the strength to face an all too familiar, timelessly evil adversary.
- This was Dalek creator Terry Nation’s final script for Doctor Who; he declined several further offers due to the extensive (uncred) story rewrite from script or Douglas Adams. He moved to the United States in 1980 and would go on to work for various television projects in America, most famously as a writer and producer for MacGyver.
- Romana tastes a mineral with her tongue to guess its composition.
- The Fourth Doctor and Romana take anti-radiation pills to sustain the contaminated environment of Skaro.
- The Fourth Doctor experiences a deja vu when landing on Skaro.
- The serial was one of the first British productions to make use of a Steadicam; due to the high cost of such a setup, nearly all the props and sets were reused, including the Davros mask.
- Michael Wisher was unavailable to reprise the role of Davros, as he was on tour in Australia. David Gooderson replaced him, but the mask was originally fitted for the slightly smaller Wisher; as a result, it suffers in appearance.
- * K9 only appears near the start of the story, explained in-story as due to an electronic form of laryngitis. K9’s absence was because the prop was unsuitable for the large amount of location filming — the production team had suffered several problems using K9 on a similar location in The Stones of Blood, and were not keen on repeating the experience. Terry Nation has said he had no desire to use K9 in his storyline; the scene (as well as other continuity gestures to Season 16) was inserted during rewrites by Douglas Adams.
- The installments of this serial are cred as episodes, rather than parts – the only serial made after The Green Death to do sao. In the next story, City of Death, it was returned to parts.
- The Movellans were in a flashback scene in The Pilot
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