The story revolves around the lost planet Shada, on which the Time Lords built a prison for defeated would-be conquerors of the universe. Skagra, an up-and-coming would-be conqueror of the universe, needs the assistance of one of the prison's inmates, but finds that nobody knows where Shada is anymore except one aged Time Lord who has retired to Earth, where he is masquerading as a professor at St. Cedd's College, Cambridge (the story features some on-location filming in Cambridge, all of which was fortunately completed before the strike). Luckily for the fate of 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 (and this is where the story really begins).
Shada was released on video in 1992, with the missing sections filled in by commentary delivered by Tom Baker. In all parts of the world except North America, the video cassette was accompanied by a facsimile of a version of Douglas Adams's script. The release was discontinued in 1996, although is still in print in the United States.
Elements of the story were reused by Adams for his novel Dirk Gently's Holistic Detective Agency, in particular the character of Professor Chronotis who possesses a time machine.
In 1983, clips from Shada were used in The Five Doctors, the 20th anniversary special. Tom Baker, the fourth actor to play the Doctor, had declined to appear in the special, and the plot was reworked to explain the events in the clips.File:BFDW shada big.jpgShada cover by Clayton Hickman.
In 2003, the BBC commissioned Big Finish Productions to remake Shada as an audio play which was then webcast in six episodic segments, accompanied by limited Flash animation, on the BBCi website. The remake featured Paul McGann as the Doctor, Lalla Ward as Romana, James Fox as Professor Chronotis, and Andrew Sachs as Skagra. Although working from the original Adams script, portions of the story were reworked to make the story fit into Doctor Who continuity. This included a new introduction, and a new explanation for the Fourth Doctor and Romana being "taken out of time" during the events of The Five Doctors. It currently remains available from the website, and an expanded audio-only version is available for purchase on CD from Big Finish.