The Sensorites was the seventh story of the first season of Doctor Who. Though The Keys of Marinus and The Daleks had both been clear examples of science fiction Doctor Who adventures, neither had specifically stated they were in the future. By contrast, The Sensorites was the first story to flatly claim a setting more than a century after the broadcast.
The third episode, “Hidden Danger”, had the dubious distinction of being the first episode of Doctor Who delayed because of programming by another BBC department. Just as series 3 and 4 of the BBC Wales version featured one-week gaps for the Eurovision Song Contest, The Sensorites was interrupted due to Summer Grandstand being extended on Saturday 4 July 1964 for special sports programming.
Narratively, certain elements of the story carried on into 21st century Doctor Who. Susan’s description of her home planet was almost directly quoted by the Tenth Doctor in Gridlock, and Planet of the Ood suggested a kinship between the Ood and the equally telepathic Sensorites.
Episode 1: Strangers in Space
The TARDIS travelers find they have landed on a drifting spaceship, and its crew is dead. The corpses are warm, even though their self-winding watches (which are powered by the movement of the wrist) say they have been dead for at least twenty-four hours. As the travelers go to leave, one of the crew members, Captain Maitland, regains consciousness. Ian Chesterton helps revive him with a device he later calls a heart resuscitator. They use this device on the other crew member, Carol Richmond. The two tell the travelers they are on an exploration mission from 28th century Earth and are orbiting Sense-Sphere. Its inhabitants, the Sensorites, refuse to let them leave orbit; they are able to control the brains of any human around them. They say the Sensorites put them to sleep but never kill them; indeed, the Sensorites feed them regularly.
As they leave, the TARDIS crew do not notice a mysterious figure burning the lock out of the TARDIS. As Ian starts to question Maitland on the future of Earth, the Doctor decides they should leave lest Ian learn too much. It is then they discover that the lock is missing. The TARDIS is permanently locked.
The Sensorites send the Earth ship on a collision course with the Sense-Sphere by taking over the minds of the pilots. The Doctor diverts this; the TARDIS crew seem to be immune to the Sensorites’ power. Carol says they have found different people are affected in different ways. She speaks of another crew member named John, who was affected more. When Maitland is asked about John, he says he’d rather not talk about it.
Later that day, Barbara and Susan are making food for the rest of the crew and ask Carol where they can find some water. Misunderstanding the directions, they go through a sensor-operated door. An unknown man, seemingly John, locks them in with him. John appears to be in a zombie-like state and shuffles towards the frightened girls. However, when he has them cornered, he collapses in front of them and weeps. Barbara consoles him and says she will make sure he gets better.
Meanwhile, outside the door, the rest of the crew realize Barbara and Susan are stuck inside with John. Maitland begins to use a cutting device to get them out. While this is happening, Carol confides to Ian that John and she were to be married when they returned to Earth. As the cutting goes on, Maitland hears a noise. It is an approaching Sensorite ship. The crew ready themselves at the controls as the ships roam into sight. Eventually the ship is surrounded and Ian is astounded to see a Sensorite at the window.
Episode 2: The Unwilling Warriors
The Sensorite at the window renders Carol and Maitland paralyzed. The Doctor awakens Maitland and reminds him of Susan and Barbara trapped on the other side of the door. Maitland continues to cut them out. In the locked area, Barbara and Susan comfort John, who is still distressed. He appears to be in almost constant communication with the Sensorites, who are trying to convince him to scare away the travelers. He refuses to do this because they are his friends now. This defiance leaves him crumpled up in pain on the floor.
John senses two Sensorites have entered the ship. He informs his new friends. Susan mentions to Barbara that she once visited a planet named Esto where there was a species of telepathic plants which screeched if you stood between them because you affected their thought pattern. With this in mind, Barbara and Susan try to overpower the Sensorites by focusing on the phrase, “We defy you”, at the same time. The Sensorites crumple to the floor.
Ian and the others open the door and release Barbara, Susan and the unconscious John. Whilst Ian is putting John to bed, John mentions the phrase “the dreams of avarice.” Ian shares a theory that John discovered something about the Sense Sphere that would prove valuable to the human race. This is why they have trapped the vessel. Maitland states that John was the ship’s mineralogist. A quick glance at his findings confirms to the Doctor that the Sense Sphere is rich in molybdenum, a precious material. As the Doctor makes this discovery the Sensorites mentally attack Carol and Maitland again. Barbara and Ian look for the Sensorites and eventually find them. Barbara runs back to the crew to ask how to lock the doors to imprison them, whilst Ian slowly backs away, threatening them with a hammer he’s found.
Barbara has to wake John to help lock the Sensorites out. Barbara notes that they were reasonably passive and never tried to harm Ian. As Barbara and Ian go back to the others to discuss what to do with their prisoners, the Sensorites start to cut through the lock. The Sensorites talk to Susan telepathically through the door, asking her to ask the others whether they can talk. This is agreed to. They inform the travelers that they have allocated an area of the Sense Sphere where the humans can live in peace but they mustn’t leave. The Doctor confronts the aliens and says that he will not live on the Sense Sphere and demands the lock to his TARDIS. The Sensorites leave to decide what to do. The Doctor notes to his companions that the Sensorites’ eyes dilated greatly in the light. This means they would be almost blind in low light. The Sensorites contact Susan again. She appears to agree to something. She informs the Doctor that she has agreed to go to live on the Sense Sphere with the Sensorites lest they kill all the humans. Two Sensorites take Susan away and the door to the control room closes.
Episode 3: Hidden Danger
The Doctor and his companions refuse to let Susan just leave and chase after the Sensorites and her. They demand her return but the Sensorites insist they need a hostage to ensure the safety of their planet. Susan agrees with the Sensorites, eager to save the lives of her friends. The Doctor shouts at her seeming submission to being kidnapped, which upsets her. When the Doctor tries to grab Susan, the Sensorites draw a weapon. Ian dims the lights which, as the Doctor previously theorized, leaves the Sensorites blinded and terrified and lets the humans slip away. The Doctor and Susan argue about whether she is adult enough to make her own decisions yet.
Meanwhile the Sensorites have brokered an agreement with Ian. Barbara and Maitland will remain on the ship with a Sensorite warrior, while the other humans go down to the Sense Sphere to talk with a Sensorite Elder. Ian reluctantly agrees but is swayed when the Sensorites say they will be able to cure John on their planet. The Sensorites also share why they are trapping them in their atmosphere. They recount a story of humans visiting the Sense Sphere. In their eagerness to leave and inform the rest of their people about the riches of the Sense Sphere, they crashed. This crash polluted the Sense Sphere with a mysterious disease which has been killing many Sensorites ever since. The Doctor promises to see if he can uncover the cause of this mysterious illness. The humans leave for the Sense Sphere.
On the surface of the mysterious planet, three Sensorites are talking. The Elder Sensorite is justifying his decision to the others, saying that the risk he is taking in inviting the humans into his palace will be rewarded if the Doctor can cure the Sensorites’ disease. The others seem dismissive of the human race, saying they are lesser beings and loud and ugly and should have been met in the mountains. The two other Sensorites act subservient in the Elder’s presence, but as soon as he leaves they doubt his leadership. The most vocal Sensorite in this uprising is the Administrator. He tells the other Sensorite he so distrusts the humans that he has aimed a disintegrator at the room where the humans are to meet the Elder to preserve the Sense Sphere’s purity.
The humans are welcomed into the court of the Elder where John and Carol are taken away to be cured, and the Doctor, Ian, and Susan are ushered in for a meeting with the Elder. Meanwhile, the Administrator is setting the coordinates for the humans’ destruction. Just as he is about to shoot, a Sensorite comes in and orders the Administrator to stop, saying the humans are harmless and only here to help. The Administrator complies reluctantly, but he also doubts the Elders’ capabilities and discusses an uprising with his friend.
Back in the court the humans are given food and water. The Elder shouts at a Sensorite servant, incredulous that his guests have not been given the same food and water as he. He sends the water back with the Sensorite, insisting he return with the Crystal Water. However, Ian has already drunk his. The Elder explains the rigid hierarchy of the Sense Sphere. Elders such as he wear two sashes, other controllers wear one and the populace are content with no sash. The Doctor asks about the difference as one rises up the social order. The Elder says the higher, the better your quality of life and the better food and drink. The Doctor asks if any of the Elders fall foul of the disease. The Elder responds in the negative.
Through this conversation Ian has been coughing and choking. On being asked, he says his throat is burning up and asks for some water. He falls to the floor, unconscious. The Elder informs the Doctor that this is the first sign of the illness and Ian is dying.
Episode 4: A Race Against Death
The Doctor and Susan try to figure out what has caused Ian’s collapse. They suspect the water, the only thing that Ian experienced that they did not. The Doctor suspects that the disease the Sensorites speak of isn’t a disease, but poison. Meanwhile two Elders discuss whether Ian’s collapse is a subterfuge of the Doctor’s to gain their trust, to seemingly cure him and then regain the TARDIS. They decide to allow the Doctor to try to cure the poisoning.
This news does not please the Administrator, who orders the scientists to murder John, whose mind they are trying to erase. An Elder berates him, saying his constant belligerence will get him into trouble. The Administrator tells the scientist that the Doctor is evil and is trying to gain the Sensorites’ trust only to betray them. John, half conscious, seems to agree with this, saying, “Evil.” The Administrator convinces the scientist the human is admitting this and tells him to pass it on to the Elders. When the scientists leave, John tells the Administrator that he meant that there is evil among the Sensorites. The Administrator says that he knew that all along and does not care for what humans think. His only wish is to wipe them from existence. The Elders hear the Administrator’s theory and decide to not allow the Doctor into his TARDIS but instead allow him access to their own laboratory. This upsets the Doctor, who shouts at them, which clearly causes them pain, but eventually he reluctantly agrees.
The Administrator talks to another Sensorite about how to reclaim the key to the disintegrator. He says that the only way that Sensorites tell each other apart is by their sashes. If he were to disguise himself as an Elder, he could get it back. The Doctor briefs the scientists on what he is looking for. He suspects the water supply has traces of atropine poison in it. The scientists tell him that there are ten different places, or districts, where the water is taken. He asks them to fetch samples for him to test. He finds only District Eight has traces of atropine. The Doctor prepares an antidote.
Meanwhile the Administrator kidnaps an Elder and his family. He takes the sash, saying he will use it to prove to the Elder that the Doctor is evil and does not intend to help them at all. He says the antidote that the Doctor has made is actually a poison and believes Ian has been falsely acting ill and he will pretend to get better. The poison will be given to the Sensorites to wipe them out, leaving the humans to harvest the Sense Sphere. The Administrator soon proves this is an effective plan when he encounters a scientist who thinks him an Elder. He tells him to give him the antidote to give it to Ian. As soon as the scientist is out of sight, he smashes the test tube on the floor. If Ian gets better, he will know that the Doctor has been lying, but if he dies then the Doctor will be proven true.
A scientist escorts the Doctor to the aqueduct to investigate the source of the poison. The scientist says they can not stay long as it is dark and their plans to light it are always scuppered. When the Doctor tells the scientist that he plans to enter the aqueduct, the scientist balks and warns him there are monsters inside. The Doctor asks if they have ever seen the monster. The scientist says they have only heard his roar. The Doctor dismisses him but speculates how convenient it is that the aqueduct is dark and noisy, two things the Sensorites cannot tolerate. The scientist returns to the Elder and tells him the Doctor has gone into the aqueduct. The Elder is disgusted, saying that the aqueduct is death to anyone that enters. Hearing this, Ian and Susan go to rescue him. The Elder, impressed with the humans’ love for each other, telepathically tells his fellow Elder that they are mistaken and the humans are noble people. This message is heard by the Administrator, who is disgusted with the Elder’s weakness, but delighted that the humans are heading to their death in the aqueduct.
Ian and Susan reach the aqueduct. The scientist gives them a radio electric light. Ian seems to be getting weaker, but still enters. Deep inside the dark aqueduct, the Doctor seems to have found what he suspected he would — Deadly Nightshade. A terrifying roar echoes through the tunnel.
Episode 5: Kidnap
The Doctor looks up in terror towards an unseen figure. Ian and Susan hear him and run towards the sound. They find the Doctor prostate on the floor, rumpled but unharmed. His only injury is a rip in his jacket. Once out of the aqueduct, the Doctor shares his theory that a Sensorite is plotting against them and the beast in the aqueduct is poisoning the water supply. Unluckily for the travelers, they have been overheard by a Sensorite loyal to the Administrator.
Back at the palace, Carol speaks to the Sensorites about John, wondering why their interference with her lover has made him so ill. The scientist explains the Sensorite brain is always open and always receiving information. The fear compartment of John’s brain is always terrified. Carol also wonders why he constantly speaks of treason and betrayal. The scientist says it must be a delusion. Sensorite society is built on trust and respect for others.
The Sensorite spy reports to the Administrator that the Doctor is onto his plot. The Administrator demands the Second Elder contact the Chief Warrior to hand over the key to the disintegrator. This the elder begrudgingly does. The Administrator goes to pick up the key in the courtyard.
As the Doctor, Ian and Susan return to the palace, they decide to ask if Barbara may join them on the Sense Sphere. They encounter the Administrator disguised as an Elder. He takes the key from the Chief Warrior. The Doctor pursues him to ask if Barbara could be brought to the Sense Sphere, but the Administrator runs off.
When the Administrator returns to the disintegrator room, he starts to set up the weapon. The Second Elder overpowers the Sensorite helper, snatches the key from the Administrator and bends it. The helper composes himself and clubs down the Elder. When the Second Elder is found to be dead, the helper is worried this will expose them, but the Administrator says this can work to their advantage. He asks if the Chief Warrior can describe the Doctor. When told yes, he takes them to the palace.
The Chief Elder receives the Doctor and his friends, his kindness underlined when he gives the Doctor a cloak to replace his coat. The Doctor offers his plan to purify the water supply. He intends to go back into the aqueduct and slay the monster within. He is interrupted by the Administrator, who tells the Chief Elder that the Second Elder has been killed. The Chief Warrior says he saw the Doctor kill him in a fight over the disintegrator key. The Chief Elder asks if he was sure that it was the Doctor. The Chief Warrior says that he could tell by his distinctive hair and he could clearly see that the Doctor took the weapon out of his coat.
Ian cross-examines the Chief Warrior, making sure he says again that he saw the Doctor’s coat. At this point the Doctor stands and reveals he is wearing a cloak. The Chief Warrior tries to change his story, but the Chief Elder sends him to prison. The Administrator apologizes to the Elder for bothering him. The Elder says he was doing exactly what he ought to. The Administrator gives the Elder the sash of the Second Elder and says he should now pick his replacement. The Doctor, seeing an opportunity to befriend another Sensorite, suggests the Administrator. The Elder agrees and gives the sash to the Administrator, who shows no gratitude to the humans.
Meanwhile John is entirely healed and reunited with Carol. He also recognizes Susan. When Susan asks what he was referring to when he spoke of betrayal he says that he can’t quite remember but is sure that a Sensorite is plotting against the humans. The Administrator pounces on this and asks whether the treacherous Sensorite is in the room. John says he is not. The Administrator leaves and John says that the only thing he remembers about the Sensorite is that there was something odd with his uniform. Elsewhere in the lab the Doctor has discovered an old map of the aqueduct which he asks the scientist to improve and bring to him in order to have a working map for their expedition. John remembers the strange feature of the treacherous Sensorite is that he had a collar. The Doctor is distraught to realize it is the Administrator that is evil.
Meanwhile the Administrator has sprung the Chief Warrior out of prison and is asking another favour of him: to neutralize the weapons given to the Doctor and Ian. The Chief Warrior says that that is easily done. He also intercepts the map of the aqueduct and corrupts it so that the explorers will get lost.
Ian and the Doctor are given the false information and the ineffective weapons by the Chief Elder and ask that Barbara be allowed in the Sense Sphere to look after Susan. The Chief Elder agrees. Ian and the Doctor decide to not tell Susan that they are going as she would only demand to come with them. They leave for the aqueduct.
Carol, John and Susan, unaware of the Doctor and Ian’s journey, are preparing a meal for the other humans’ return. After a long wait, Carol goes to look for them, but, as she crosses the courtyard, a hand grabs her.
Episode 6: A Desperate Venture
Carol is brought into the disintegrator room. She is forced to write a letter to John and Susan saying she has gone to the space ship. The Administrator does not know that Barbara has been brought from the ship and can prove Carol was not there. When the humans get the letter, they grow more suspicious of the Sensorites. They show the letter to the Chief Elder, who says that the letter is obviously forged. They also suspect something has happened to the Doctor and Ian but the Chief Elder says that they have gone into the aqueducts and did not want to worry their friends. Susan points out the ink on the letter is still wet. Carol must be near. The Chief Elder suggests the disintegrator room. John goes to investigate and enters as the Chief Warrior threatens Carol with the disintegrator. While John distracts him, Carol disarms him and the Chief Warrior is imprisoned again.
In the palace, the Administrator is talking to the Chief Elder, acting concerned at the Chief Warrior’s escape. He asks if the Chief Warrior has implicated anyone else.
In the aqueduct the Doctor and Ian discover something moving ahead of them. As Ian edges forwards to investigate, a human attacks them. They scuffle and the man escapes. All that is left is a badge in the shape of a rocket ship.
Back at the palace it is decided that, since the Doctor’s weapons and maps are faulty, another party should enter the aqueduct to rescue them. Barbara and John will go in. Susan will stay behind and guide them by transmitting her thoughts to the Sensorites — Barbara borrows one of the Sensorites’ communications tools.
Back in the aqueduct the Doctor and Ian pursue the humans, but are then surrounded by them. They take the two men to their Commander. The Doctor suggests that these are survivors of the last expedition to the Sense Sphere. They are curious to know if the men are alone. They say they are. As they are taken deeper into the aqueduct, the Doctor marks the wall in case they need to escape. Barbara and John take this to be a sign to follow them.
When the two men meet the Commander, he explains they are survivors of the first expedition. The ship that crashed all those years ago were militia deserters. The Commander blew up the ship before they escaped. His group has been poisoning the Sensorites to wipe them out and harvest their planet. He seems to believe his men are at war with the Sensorites. At this point one of the men comes in to report more people coming. This angers the Commander, who believes the Doctor has lied to them. When Barbara and John turn up, the Doctor convinces the men they are a victory party celebrating the glorious human victory. They head to the aqueduct’s exit. Barbara surreptitiously contacts the Sensorites to position themselves at the mouth of the aqueduct with their weapons, where they seize the humans.
Afterwards, at the Palace, the First Elder has given permission for Maitland to take the astronauts back to Earth where they can receive medical treatment, and announces that the Administrator has been banished to the outer wastes of the Sense-Sphere for his crimes, never to return. The TARDIS lock has also been replaced and the travelers are free to leave.
Some time later, in the TARDIS, the travelers are watching on the scanner an image of the spaceship disappearing into space on its way back to Earth. Ian comments that at least Carol, John and Maitland know where they are going. This angers the Doctor, who says that wherever they land next, he is leaving Ian there.