The Doctor Who story "Robots Of Death" is a murder mystery, even though it's obvious right away who's killing tons of people on board a claustrophobic mining vessel picking its away across the ore-rich sands of the planet Kaldor. The identity of the murderer is right there in the story's title. The whodunnit aspect is much more about what's making these robots kill people, and what does it mean for a society that's utterly dependent on robots? The first question has an utterly, delightfully demented answer. The second one, you'll be pondering for hours after you watch it.
Let's take the second question first. Kaldor's relationship to its robot workforce is akin to our society's relationship to the automobile. Over the course of the 90-minute story, we learn a lot about Kaldor's culture and history, without anyone ever pausing to lecture us - the worldbuilding in "Robots Of Death" is so rich and clever, writer Chris Boucher felt the need to return to it in a sequel novel, Corpse Marker. And there's been a whole series of audiodramas based in the capital, Kaldor City. (The novel's underwhelming, and I tried to get into the audios, but couldn't.)
In any case, we learn that Kaldor was colonized by humans within fairly recent memory, and there's a lingering class system that puts the earliest settlers (the "founding families") at the top. (The sandminer's captain, Uvanov, is lower class and deeply resents his upper class crewmember, Zilda, who he thinks looks down on him. She, in turn, blames him for the death of her brother on a previous tour. More on that later.) A good deal (possibly all) of the planet's surface is covered with ugly, windswept desert, prone to horrible sandstorms which can cut you to shreds in seconds. (As the Doctor nearly learns first-hand.) And those sandstorms stir things up enough to bring precious ores (yes, even lucanol!) to the surface, where a squat, lumbering sandminer can suck them in and refine them. The work is grindingly awful and stressful, because you have to jump on sandstorms the moment you find them, if you want to meet your quota. So you need the robots to help you manage.
But Kaldor doesn't just depend on the robots for the sandmining that (apparently) fuels its economy. Every aspect of life back in Kaldor City is robot-centric: they're the masseurs, the nannies, even the cops in some cases. Perhaps in a reflection of the rigid class system among Kaldor's humans, the robots are divided into three classes as well: the Dums (who can't speak), the Vocs (who can), and the rarer Super-Vocs (who are intelligent.)
So the humans of Kaldor are terrified of their robot servants, deep down, even though they depend on them. (Or maybe partly because they depend on them so much.) This affects everyone, to some extent — there's a great scene early on, where someone is getting a massage from a robot, while a guy sitting nearby talks about how a robot masseur once went wrong and ripped a client's arm off. But some people suffer from it most keenly than others — one guy, Poul, suffers from "robo-phobia," an unnatural (but understandable, it turns out) fear of robots. When he finds a robot with human blood dripping down its sleeve, Poul starts to lose his marbles. Too bad he's the guy sent to investigate the murders in the first place. We also learn that Zilda's brother didn't die due to Uvanov's negligence — he suffered an attack of robophobia and ran outside the sandminer to escape the robots, dying instantly.
Really, there's an undercurrent of robophobia running through this entire society, which desperately needs robots to survive but can't trust them. In one fantastic scene, Leela asks the Doctor what will happen if it does turn out that robots are murdering people. In his wonderfully casual/brutal way, the Doctor says "I should think it's the end of this civilization." Ooh, snap!
Of course, the robots have all the usual Asimov-ian safeguards, about obeying humans and never harming them. It just turns out that if you're smart enough — and willing to jam a laser probe into a robot's brain — you can overcome those.
As Fiona Moore points out, the robophobic Poul and the robot-loving Capel are just two sides of the same coin:
Both Poul and Capel (who are interestingly both named after science-fiction writers) are outsiders in disguise; their true "identities" are also both tied up with a secret held by one or more of the robots on the Mine. Visually, Capel's death echoes Poul's descent into madness an episode earlier; like Poul, Capel falls to his knees before a robot, screaming senseless phrases in his terror. Poul's quick denial that a robot could be responsible for Chub's death also finds a parallel later in Capel's quick denial that robots are dependent on humans for their existence. The two characters thus have more in common than simple madness.
Taren Capel? Never heard of him.
Capel's madness, like Poul's, is therefore not innate, but imposed from the outside. In the scene in which Leela finds Poul hiding in the robot morgue, Poul in his terrified delirium attempts to betray her to the robots, believing that if he lets her help him the robots will view him as an enemy. Poul also implies that he believes himself to be immune from attack by the robots as long as he keeps still and hidden. Similarly, Capel's behaviour could almost be seen as an attempt to ingratiate himself with the robots; he dresses himself like them, repeatedly calls them "my brothers" and offers them a help they do not request. At the end of the story, as a robot's hands close on his throat, he cries out, not "I am your brother," but "I am the master," again implying a terrified attempt to assert control over an unstoppable force. His murder at the hands of a robot parroting the phrase "kill the humans" must be for Capel the most frightening and humiliating death imaginable. One of the few things we know about Capel is that he was raised by robots; for most people, our images of strength and control are drawn from our early experiences with the people who raised us (again, the Doctor's remark about Dask not being half the robot his father was recalls this). By drawing parallels between Poul and his quarry, Boucher has thus hidden the key to Capel's madness in plain sight: it is not Capel's megalomania, but his robophobia, which causes the unfolding of the events on Storm Mine Four.
I hadn't actually thought about the idea that Capel, the robot supremacist, is actually just displacing his own internalized robophobia, but it does make a kind of sense. Especially in his disguise as Dask, the sandminer's robot expert, Capel is so keen to argue that robots can't kill — while he's actually proving they can.
But to me, the really interesting thing about Capel's robot revolution is that it's doomed from the start. Capel wants to see robots break free from their human masters, but he never asks the robots what they want. In fact, the robots in the story never seem to express any particular desires — even the hyper-intelligent ones like Super-Voc 7 and the undercover robot agent D-84. They want to do a good job, and they want to fulfill their function, but there's never any hint that the robots are cherishing unfulfilled desires.
So Capel doesn't empower the robots to kill — he programs them to. They have as little choice about that instruction as they do about any other. And he's only able to get them to do this (as I mentioned) by jamming a laser probe into their heads, thus committing violence on them in the name of getting them to commit violence.
Is "Robots Of Death" really the greatest killer-robot story of all time, as I cheekily claimed in the headline? Actually, it really is possible — it does what the greatest killer-robot stories do, which is to tell us something new about our codependent relationship with technology. All of the humans in the story are painted to look like robots, like Capel, just in a lesser way. And they're all terrified of robots, like Poul, just in a lesser way. In the end, "Robots Of Death" tells us that the more powerful our technology becomes, the more we'll fear it — and the more we'll shape ourselves to become like it.
Luckily, "Robots Of Death" was one of the first Who stories to come out on DVD, and I'm pretty sure you can find a used copy cheap. Enjoy!