The Doctor: When I was on the river, I heard a strange babble of inhuman voices. Didn't you, Romana?Filming on "Shada" ("SHAH-duh"), which was interrupted by the 1979 BBC strike, was never completed. It remains the only story of Classic Who that has never aired. But Douglas Adams scripts aren't so common that they can be discarded so easily, and eventually three official versions saw the light of day: a 1992 filmed version cobbled together out of the existing bits, with linking narration provided by Tom Baker; a 2003 Big Finish-produced audio (also available for free with some web-animation) with Eighth Doctor Paul McGann as the story's Doctor; and a 2012 novelisation by Gareth Roberts, based on the final versions of the scripts. Clips from this episode were also used in "The Five Doctors" to Fake Shemp Tom Baker.For extra credit, spot the plot elements that Adams recycled into Dirk Gently's Holistic Detective Agency.
Professor Chronotis: Oh, undergraduates talking to each other, I expect. I've tried to have it banned.
One day, the Doctor gets an invitation from Professor Chronotis, a retired Time Lord posing as an eccentric old Cambridge don. He and Romana drop by St. Cedd's College, Cambridge, in 1979.Chronotis is extremely old, even for a Time Lord, which makes his memory spotty and unreliable... but after some gentle prompting, he eventually remembers that he'd wanted the Doctor to take a certain book back to Gallifrey. No ordinary book, this, but an ancient relic from the days of Rassilon, the founder of Time Lord society, and possibly (read: almost certainly) full of uncertain and dangerous powers. The three Time Lords begin to search Chronotis' flat for it.Unfortunately, Chronotis has already forgotten that he'd just that morning lent it out to physics student Chris Parsons — who's taken his new toy over to the lab to examine it, with baffled fascination, and even asked his girlfriend Claire to come have a look.Even more unfortunately, someone else is after the book, too: a guy named Skagra, and with a name like that he's got to be evil. Skagra's putting the finishing touches on a brain-in-a-jar — actually, a collection of great minds, whom he'd lured into working with him under false pretenses and then mind-napped — and just needs one more mind. Specifically, he wants the mind of legendary Time Lord criminal Salyavin, who was said to have the power to project his own mind into other minds; with this power in Skagra's brain jar, he'd be able to control the rest of the universe. Salyavin is imprisoned on the prison planet of Shada, whose location has been lost for centuries, but Skagra is convinced that the directions are in Chronotis' book.By the time Chronotis remembers Chris Parsons' name (going through the alphabet until he reaches "Y"... "Young Parsons!"), Skagra has parked his spaceship outside town and gotten a lift to St Cedd's. The Doctor's just left, though — he's borrowed a bike and gone off to fetch Chris from the physics lab, little realizing that the guy he nearly crashed into on the way was Chris himself, on his way to see Chronotis to ask about the book.The Doctor does meet Claire at the lab; with her in tow, and in possession of the book, they return to Chronotis' flat — to find the old professor dead, killed by Skagra while Romana was in the TARDIS looking for milk for the tea. With the help of some Time Lord technology, Chronotis manages to convey a final message: watch out for Shada.Shada turns out to be a prison planet, and the gang soon all find themselves there. The Doctor is (of course) captured by Skagra, fibs his way through an interrogation by pretending to be really dumb, and is promptly killed by a very annoyed Skagra. However, the Doctor knows enough about this sort of thing to relax his mind at the last moment, meaning Skagra only gets a copy of his memories and the Doctor continues to live. He convinces Skagra's ship that, since he's now dead, he's not a threat anymore and the ship can freely listen to him. The ship is a bit confused, but rolls with it.Professor Chronotis, meanwhile, is Only Mostly Dead and uses Claire to track down the others (using his TARDIS, which turns out to be have been his living room all along). He also turns out to be Salyavin. Once the Doctor rejoins the plot (after taking a short unprotected trip directly through the vortex and MacGyvering one very silly mind-shielding helmet), he's able to mind-control Skagra's golems and prevent the Assimilation Plot. He and Romana decide to simply drop Chronotis/Salyavin off back home, since rumours of his great evil were probably for the most part just exaggerated nonsense. The Doctor wonders if people will say the same about him someday.