Written by Don Houghton
Directed by Timothy Combe
Arriving at Stangmoor Prison, the Doctor and Jo attend a demonstration of the Keller Machine, a device that supposedly removes all negative emotions from its subjects. It's being used to forcibly reform hardened criminals. Troubled by the implications of this machine, the Doctor's fears are borne out when its latest subject, Barnham, collapses after his treatment.
Back in London, the Brigadier is handling two high-pressure situations. First, UNIT is in charge of security for a tense World Peace Conference, made even more volatile following the disappearance of vital documents and the death of the Chinese delegate. Second, the Brigadier has also sent Captain Yates to handle the transport and destruction of a nuclear powered Thunderbird missile loaded with illegal nerve gas.
Back at Stangmoor, things are escalating out of control. There have been several deaths in the vicinity of the Keller Machine, all seemingly caused by impossible physical manifestations of the victims' worst fear. In the middle of investigating the Machine, the Doctor is called back to assist the Brigadier in the intrigue at the Conference.
The Doctor and the Brigadier uncover and prevent an attempt by Captain Chin Lee, the aide to the Chinese delegate, to kill the American delegate. The Doctor discovers that Lee is under the hypnotic control of the Master, and he also learns that the Master is also known as Professor Emil Keller, inventor of the Keller Machine.
The Master has already arrived at Stangmoor, where he uses the power of the Keller Machine to start a riot that results in the inmates seizing the prison and taking hostages, including Jo. The Machine stores all of the evil impulses it has extracted, but is not actually just a machine, but rather a house for a malevolent alien parasite that grows in power as it feeds on negative impulses. Offering the convicts the chance to disappear anywhere in the world, the Master enlists their aid to steal the Thunderbolt missile. The Master's ultimate goal is to use the missile to destroy the conference and start WWIII.
Don Houghton wrote the scripts for the best story of the previous season, Inferno, so it makes sense that The Mind of Evil is similar in tone. Indeed, this serial's dark atmosphere, grittier feel and reliance on down-to-earth suspense rather than fantastical adventure, makes it very much a companion piece to Season Seven.
The structure of the story doesn't quite work, it must be said, with disparate elements of the Master's scheme (the parasite and the prison, the conference, the missile) not really dovetailing into a cohesive plan as well as they should. The amount of coincidence involved is more than a little staggering, and the result is that the scripts feel like Houghton had three separate ideas he liked and then tried to shoehorn them into one plot. But the disparate elements are certainly compelling, and the fact that the action is split between the prison, the conference and then the missile heist, means that you don't get the padding and longeurs that you often find in a six part story.
The initial threat of the Keller Machine is by far the most compelling element, as it allows the exploration of the vulnerabilities of both the Doctor and the Master. Jon Pertwee was such an implacable force of nature during his era, even at this early stage, so it's fascinating to see his veneer of authority stripped away and watch him admit that he cannot defend himself against the powers of the machine. It's genuinely unsettling to see him so terrified, a fact that unnerves even the Master. Delgado similarly delivers a great performance. He begins like a Bond villain, chomping on a cigar in his Rolls Royce, handily in charge of everything going on, further cementing him as the Doctor's equal. But as things escalate, we also get to see him become more and more unnerved by this alien he's using, and the scene in which his greatest fear is revealed to be the Doctor mocking him is justly lauded. Yes, in the end, his plan doesn't really make sense, but when it's anchored to a performance this good, and when the sparks between him and Pertwee are this fun to watch, who cares?
The conference is the part that feels the most like wheel-spinning, and the prison goes from riot to riot, but it's all executed so well that it never feels like padding. Timothy Combe tops himself, pulling off a very technically demanding and expensive script with style and visual ingenuity. Take for instance the scene in which the Keller Machine breaks free of its restraints. Using a whirling and zooming camera and crashing scenery, he pulls off the considerable feat of making a inanimate object look dynamic. In fact, he makes a box seem like a terrifying object throughout, no easy task. The scenes of chaos at the prison are all staged extremely well, and he handles the intense, yet quiet, moments between the Master and the Doctor equally well. His action set pieces are among the best ever filmed for the series, with the missile high jack topped by the superb assault by UNIT on the prison. It's clear that he went way over budget, but every penny is right there on the screen.
Jon Pertwee still seems to be overplaying the rudeness and ill-temper of the Doctor too much for my taste, though it's a lot better than in Terror of the Autons. Most of what leavens this is the reactions of the supporting characters, particularly Courtney's Brigadier, who takes all of the Doctor's jibes with a wry sense of humour that lets the audience know that the Brig doesn't take these fits of pique too seriously. This attitude is also mitigated by the superb performance of Pertwee in the scenes where the Doctor is assaulted by the parasite, and in the lovely quiet scenes where he's locked up with Jo.
As for Jo, after my drubbing of last episode, I'm happy to report that she's amazing in this story. Yes, she doesn't play that active a role, but she's shown to be kind and caring, intelligent and capable. The scene where she pretty much single-handedly thwarts the first prison riot is great, demonstrating that yes, she is a capable UNIT agent. Her relationship with Barnham is sweet and the rapport she has developed with the Doctor is touching and honest. This is the Jo that will become one of the all-time great companions, and Katy Manning is fantastic throughout.
The Mind of Evil is a favourite of the era, and will be hard to top as the best of the eighth season.