The Doctor visits his old Time Lord friend Chronotis in Cambridge, 1979. But the ruthless Skagra has also arrived to retrieve a book that will help unlock one of the Time Lords' greatest secrets: what is Shada? Filming for this story was never finished, and in this version the unfilmed material is completed via animation.

• BBC
• BBC Worldwide
• Tom Baker
• Lalla Ward
• David Brierly
• Christopher Neame
• Daniel Hill
• Denis Carey
• Victoria Burgoyne
• Gerald Campion