The TARDIS’ crew find themselves in what appears to be a moving object. Ian muses that “we are different from when we started out with you.” The Doctor agrees, saying that “it’s turned out to be a great spirited adventure.” Although Barbara notes that nearly every time they leave the TARDIS they get into trouble, the Doctor wants to head out to see where they are. Outside they find they are on a spaceship where seemingly the crew, a woman and a man, has recently died with no visible signs of wounds. Before they can return to the TARDIS, they find the captain of the ship, Maitland, who gives Barbara a device that revives the woman, Carol. Maitland explains that the crew isn’t dead but is in stasis. From conversation with Maitland the Doctor and the others learn that the ship is from Earth and that it’s the 28th century. Carol interrupts to urge them to leave, since they’re all in danger. At the Doctor and Barbara’s prompting, Maitland explains that they’re oribiting a planet called the Sense-Sphere, and its inhabitants, the Sensorites, have some mysterious form of control over the ship as well as the crew’s minds. The Sensorites have trapped the ship in space and placed them in stasis, but will not harm them; in fact, they make sure the crew remains well-nourished. At Maitland’s insistence, the Doctor and the others prepare to leave, discovering to their horror that the Sensorites have removed the TARDIS’ opening mechanism, effectively sealing the TARDIS.
Before they can think about the situation, the ship begins to be pulled toward the Sense-Sphere. The Doctor manages to help pilot the ship to avoid collision and theorizes that the near-crash was an intimidation tactic. While they go to retrieve some water, Susan and Barbara are trapped on part of the ship by the third member of the ship’s crew, the mineralogist John. Carol tells Ian that John was her fiancee and that the Sensorites probed him telepathically far more than either her of Maitland, making him dangerously insane. However, John is comforted by Susan’s resemblance to his sister, but soon collapses, claiming that the Sensorites are trying to force him to frighten them. A group of Sensorites come back to the ship, driving John into hysterics. Meanwhile Susan tells Barbara that they can use their own thoughts through concentration to disrupt the Sensorites’ control of John as Maitland and Ian manage to force the door open and put John to rest.
The Doctor and Ian suppose that John must have discovered some kind of rich material on the Sense-Planet and they attacked to keep it secret. Looking over John’s records, the Doctor realizes that the Sense-Sphere’s surface is rich with molybdenum. When Ian runs into a pair of Sensorites, he sees that they are non-aggressive and as frightened of the humans as they are of them. Barbara, John, and Ian lock various doors on the ship to isolate themselves from the Sensorites, who telepathically contact Susan. Now able to communicate, the crew agrees to let the Sensorites in. They tell the crew that they do in fact fear having their planet exploited for its molybdenum, that humans have hurt their people before, and that they expect them to remain on the Sense-Sphere. The Doctor angrily tells them off but, even then, the Sensorites insist that they do not wish to harm them. The Doctor demands the return of the TARDIS, threatening retaliation unless they relent (“I don’t make threats, but I do keep promises!”) Once the Sensorites leave, the Doctor tells the crew and his companions that he observed that the Sensorites’ eyes are totally unaccustomed to darkness. The Sensorites contact Susan again, and she agrees to accompany them down to the Sense-Sphere to avoid having everyone killed.
Before they can leave, after an argument the Doctor forces Susan to join the others again and shuts down the lights to intimidate the Sensorites into submission. Subdued, the Sensorites explain that once an expedition of humans arrived on the planet, had an intense argument between themselves, and when they left their ship exploded. Since then, Sensorites have been dying from an unknown illness in greater numbers. Ian, Susan, Carol, John, and the Doctor depart for the Sense-Sphere, to help the Sensorites diagnose the cause of the sickness in exchange for the return of the TARDIS’ opening mechanism, the liberation of the ship’s crew, and the treatment of John’s mind. Despite the willingness of the Sensorites’ leader, the First Elder, to work out an understanding with the humans, another leading Sensorite, the “city administrator”, arranges to have them killed with a weapon called the disintegrater, but he is stopped by the First Elder’s second-in-command, the Second Elder, who is impressed by the civility of the visitors. At the talks, the First Elder assures them that they did not intend to drive John insane. During the conference Ian, who drank water provided from the city aqueduct, complains that his throat is burning and passes out. The First Elder tells the others that Ian is showing the same symptoms of the illness striking down his people. The Doctor deduces that water from the aqueduct must be the cause of the “illness”, which is actually a poison. Using the Sensorites’ scientific resources, the Doctor is able to devise an antidote. The administrator is convinced that Ian is only pretending to be ill and the antidote is actually a poison the Doctor plans to administer to the populace and sets out to sabotage the Doctor’s “plans” by abducting the Second Elder and disguising himself as him.
The Doctor investigates the aqueduct, despite one of the Sensorites’ warnings that there are monsters there. Ian, who has been treated with the antidote, takes Susan to follow the Doctor into the aqueduct. They find the Doctor wounded with claw-marks, after being attacked by something he did not see, and claiming that the water had been deliberately poisoned. The Second Elder is killed by an ally of the administrator while trying to escape and stop the administrator from using the disintergrater, giving the administrator the opportunity to try to frame the Doctor for the Second Elder’s death. However, Ian is able to prove that the accusation is false, but the administrator acts quickly to convince the First Elder that the Second Elder had been behind the plan. The First Elder decides to promote the administrator to the vacant position of Second Elder. A little later John, who has recovered his sanity under the Sensorites’ treatments, is able to help Susan, with his memories of his former telepathic impressions, piece together that the former administrator is actually their Sensorite enemy.
Ian and the Doctor set out to the aqueduct with defective weapons and a sabotaged map, courtesy of the new Second Elder, who promptly abducts Carol and forces her to write a letter to John claiming she returned to the spaceship. Since Barbara was on her way down from the ship, Susan and John quickly figure out that Carol had actually been kidnapped. John rescues Carol and the Second Elder’s ally is arrested, eventually leading to the Second Elder’s downfall. Barbara and John go follow the Doctor and Ian into the aqueduct, with Susan guiding them telepathically with the help of the Sensorites’ technology, while the Doctor and Ian discover that the water had been poisoned by the three survivors of the last human expedition to the planet, who have been operating under the commands of their hawkish leader and who were responsible for the explosion that killed their comrades. All of them have gone insane and believe that they’re the spearhead of a human invasion of the entire planet. After being reunited with Barbara and John, they trick the leader into thinking that Earth forces have conquered the Sense-Sphere and hand them over to the Sensorites. Maitland, Carol, and John are allowed to leave to return to Earth. On the TARDIS, Ian blurts out, “At least they know where they’re going!” The Doctor grumbles, “So you think I’m an incompetent old fool, do you? Since you are so dissatisfied, my boy, you can get off the ship and the next place we stop I will take you off myself, and that is quite final.”
The Doctor mentions that he once met Henry VIII. Naturally the encounter did not go well. Susan also mentions being on a planet called Esto, where there were plants that transmitted thoughts to each other (like The Green from the DC Universe?).
There’s quite a bit established concerning the Doctor’s ethics, points that have more or less been consistent over the years and the various incarnations. The Doctor says he doesn’t like using weapons “at any time” while he not only expresses opposition to the death penalty even in extreme circumstances, but believes that the banning of capital punishment is a requisite of a truly advanced society.
The Doctor comments that Carol is “only a few years older than Susan”, so apparently Susan is young even by human standards, which could be a handy explanation for Susan’s behavior in previous episodes (for instance, Time Lord children take even longer than human offspring to become mentally and emotionally mature, so in human reckoning Susan is, relatively speaking, more like a ten-year old).
The Sensorites appear again, sort of, as the Ood in the 2005 series. It’s even explicitly spelled out in “Planet of the Ood” that the Ood and the Sensorites are related species and that the Ood’s homeworld, the Ood-Sphere, is astronomically close to the Sense-Sphere.
On top of all that, there’s more established about the Doctor and Susan’s homeworld than in any previous serial, even “An Unearthly Child.” Even though it is explained that the particularities of the Sensorites and the Sense-Sphere have made her far more sensitive telepathically than usual, dialogue does spell out that Susan was born with telepathic senses. Whether or not it’s also implied here that the Doctor, and by extension their entire race, is telepathic too is debatable; certainly the Doctor’s own telepathic capabilities or lack thereof do not play a role in the plot. Still, continuity nerds should take note of the fact that the Doctor doesn’t seem all that surprised that Susan has such abilities and even suggests that when they return home Susan should be trained to develop that power even further, all hinting that telepathy does exist in their species but, like pitch perception, some people are just born with more of it than others. At any rate, it’s been established, especially in the 2005 series, that the Doctor is indeed capable of telepathic feats, and the audience has already learned in “The Edge of Destruction” that the TARDIS can affect its passengers telepathically as well.
Although what would become Gallifrey hasn’t been named yet, Susan does describe her homeplanet as being “a lot like Earth” but “the sky is a burnt orange” and “the leaves on the trees are a bright silver.” Later descriptions and visual representations of Gallifrey have followed up on Susan’s explanation (with the exception of “The Three Doctors”, where a blue sky is seen over a Gallifrey locale). She also says “it’s been ages” since she or the Doctor have seen their planet, which, in regard to the mystery of why the Doctor and Susan, at least suggests that Susan was old enough to have memories of her home (of course, there’s always the counter-argument that Time Lords might able to remember things for life even in infancy. If Vulcans can do it, why not Time Lords?).
Our Future History
By the 24th century all of southern England becomes one giant metropolis called “Central City”, making the name London archaic, and at some point Big Ben ceases to exist for an unexplained reason.
(When Barbara asks Maitland what the problem is and offers to help)
“No, no, Barbara. I’ve learned not to meddle in other people’s affairs years ago.”
“Now, now, now, don’t be absurd. There’s not an ounce of curiosity in me, my dear boy.”
(The Doctor repeats Barbara’s question, as Ian and Barbara laugh)
It’s funny how this episode ended up addressing two points I raised concerning the last episode. For starters, the Doctor proves he hasn’t tempered his bite, brutally shooting down Susan’s one moment of selfless heroism (even if he did have every reason to) and bellowing at the Sensorites, even after he knows that they’re (mostly) benevolent and that they’re sensitive to loud noises. Second, Susan comes across as a more well-balanced, capable character, enough so that it’s tempting to wonder whether or not the showrunners were responding to the audience or to Carol Ann Ford’s complaints. Susan’s status as the inexperienced teenager of the group still comes into play, but in a more satisfactory way that doesn’t leave her looking like a hysterical idiot. In fact, as right as the Doctor may have been in stopping her from completely trusting a pair of then-unknown aliens, Susan turns out to have had a point, and she does get to be the hero of the episode in several respects. It remains to be seen if this better, smarter interpretation of the character sticks around (judging from some reviews of future episodes I glanced over, it does not).
This is the sort of story that will become de rigeur as the series evolves, especially the now familiar “trapped by largely unknown forces” scenario, but, compared to “The Daleks”, it seems quite fresh. This is especially because it breaks with what was already a sci-fi cliche by having the invaders turn out to be humans from Earth, although some of the potential edge is taken off by having the “invaders” turn out to be deluded and insane. Admittedly it does take the “Star Trek” way around exposition by conveniently reducing an entire planet to one government and one society (the Sensorites talk about “the city” with virtually no references to anything else on the planet), yet the Sensorites’ society is actually fleshed out, with more than plot-driving details. It makes sense for a species that has evolved telepathy to be vulnerable to loud noises and to have a culture where trust is universally assumed rather than something to be earned and where there are no birth-names, only titles. In this respect “The Sensorites” has a definite advantage over the better known serial from the same season, “The Daleks.”
It’s also fun that the Doctor and his companions actually comment on the changes in their characterization since the show began. It makes the show’s world seem more organic and maintains the already strong emphasis on character, which helps make even this decades-old serial stand out against the reiterations of the formula seen in other sci-fi franchises and in later episodes.