Derek Pollitt

Shada: a prison built by the Time Lords for defeated would-be conquerors of the universe. A scientist named Skagra needs the help of one of the prison's inmates. He finds nobody knows where Shada is anymore, except one aged Time Lord who has retired to Earth, where he is a professor at St Cedd's College. Luckily for the universe, Skagra's attempt to force the information out of Professor Chronotis coincides with a visit by the professor's old friend, The Doctor.

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.

The TARDIS narrowly avoids becoming engulfed in a cobwebby substance in space. It arrives in the London Underground railway system, the tunnels of which are being overrun by the web and by the Great Intelligence's robot Yeti. The time travellers learn this crisis was precipitated when Professor Travers, whom they first met in the Himalayas some thirty years earlier, accidentally caused one of the Yeti to be reactivated, opening the way for the Intelligence to invade again.

Jamie tries to evade Yeti in the tunnels of the London Underground. Meanwhile, The Doctor and Victoria meet a potential new ally - Colonel Lethbridge-Stewart.

The adventures of The Doctor, a time-traveling humanoid alien known as a Time Lord. He explores the universe in his TARDIS, a sentient time-traveling spaceship. Its exterior appears as a blue British police box, which was a common sight in Britain in 1963 when the series first aired. Along with a succession of companions, The Doctor faces a variety of foes while working to save civilizations, help ordinary people, and right many wrongs.