Originally broadcast in 1964, The Keys of Marinus is a six-episode arc that features the doctor's original traveling companions, science teacher Ian Chesterton, history teacher Barbara Wright, and the doctor's granddaughter, Susan, who is given to screaming at the first sign of peril. Hartnell's doctor is a sprightly curmudgeon who relishes adventure and mystery, which he finds after the group lands on Marinus, an island of glass surrounded by a sea of acid. Doctor and company are compelled to retrieve four microcircuits that are the keys to the Conscience of Marinus, a computer that has eliminated evil from the minds of men (except apparently the evil Yartek and his web-suited Voords, who want to seize the machine). Their quest takes them most memorably to "a planet of the most contented people" (beware the brainwashing powers of the "mesmerent"), another world overrun by plants, and finally a city where Chesterton, framed for murder, is considered guilty until proven innocent--by the doctor, of course. As is characteristic of this series, the special effects are a hokey hoot and the actors sometimes step on each others' lines. Hartnell vacationed during production and is absent for two episodes. But this is a surprisingly prophetic cautionary tale: it may be good to heed the doctor's prescient observation that "man was not made to be controlled by machines." If you have yet to make an appointment with the doctor, perhaps the episodes featuring Tom Baker--the fourth and most popular of the doctors--are a more accessible introduction. --Donald Liebenson
Using travel dials, wrist teleporters, they go to where the four microcircuit keys are, first to the luxurious city of Morphoton, "sensuous, decadent, but pleasant" with kind hospitable people. Yet is all this luxury real?
Accompanied by Sabetha, Arbitan's daughter, and Altos, her love interest, the Doctor has the brilliant idea of splitting up. He goes to the civilized city of Millennius, while Ian and Barbara search a place where the vegetation is very dense and "when the whispering stars, it's death." Altos and Sabetha land on an icy area where they encounter a trapper Vasor, who isn't all he seems. On Millennius, Ian is falsely accused of murder and the Doctor becomes Sherlock Holmes in order to save Ian. A city where one is guilty before proven innocent cannot be all that civilized.
Ian shines the best in this story, as he comes out as reliable, trustworthy, and brave. One of his best hours. The interplay between Barbara and Susan remains. Susan trusts Barbara to tell her what she heard in the forest in the same way she tells her of the hand that touched on in the petrified forest in The Daleks. Barbara's her usual reassuring self here.
George Coulouris (Arbitan) is best known as the man who takes Kane from his parents in Citizen Kane and as the doctor in Murder On The Orient Express. Fiona Walker (Kala) would reappear in Who's 25th anniversary story, Silver Nemesis as Lady Peinforte.
The ultimate theme of this story is given in Doctor's final piece of advice to Sabetha: "I don't believe that man was meant to be controlled by machines. Machines can make laws, but they cannot be made to preserve justice. Only human beings can do that."
William Hartnell did not appear in Episodes 3 and 4 so he could take his holiday, yet he was credited for both episodes per his contract. A similar thing would also happen to Jacqueline Wright in The Web Planet a season later.
The Keys Of Marinus is interesting in that many concepts of the show later found its way to future Who stories. For example, the search for the four keys was expanded in the six Key To Time stories of 1978-79. The concept of the Conscience as a machine that bars evil, plus the five microkeys with a permutations of numbers and symbols was revisited in The Keeper Of Traken. An acid pool is also encountered in The Web Planet. Vegetation tha attacks appeared in The Seeds Of Doom. And it was written by the Chief Dalek himself, Terry Nation. Thank goodness this Hartnell story survived the BBC purge, because it's well worth it.