The Mutants was the fourth story of season 9 of Doctor Who. Its narrative inspiration was very similar to that of Colony in Space. Whereas Malcolm Hulke had based the earlier story on the struggle of Native Americans against European settlers, here Bob Baker and Dave Martin explicitly based their story on South Africa and the segregationist policy of Apartheid, which had also inspired Ian Stuart Black’s The Savages. By the recording, however, director Christopher Barry had de-emphasized the political allegory in favor of the story’s science fictional elements. One such element came from an unused 1966 Barry Letts story submission, itself entitled The Mutant. Forming the main plot of the later episodes, this Letts-inspired subplot focused on a species maturing in radically different physiologic phases, like a butterfly.
On the polluted world of Solos, an old man flees through the desolate remains of a forest. Screaming, “Mutt! Mutt!”, the Marshal of Solos chases the old man, followed grudgingly by Stubbs and Cotton. Pausing to pick up the Marshal’s dropped oxymask, essential in the toxic Solonian air, Stubbs and Cotton briefly lose their commanding officer in the thick mist. They find him standing over the corpse of the old man. The dead Solonian has jagged deformities on his back. The Marshal orders his men to log it: another dead Mutt.
Back on 20th century Earth, the Doctor and Jo are interrupted by the sudden appearance of a message pod from the Time Lords. His TARDIS is already programmed with its destination and, despite his objections, Jo joins the Doctor as it sets off for Skybase One in orbit of Solos. Arriving in the Skybase’s broom cupboard, the Doctor explains to Jo that they are at the end of the Earth Empire’s reign.
At the Skybase’s Trans-mat facility, Solonians are beaming up from the planet to attend a conference with the Overlords, the planet’s colonists from Earth. Ky arrives and is greeted by Varan. The greeting is anything but friendly. Ky makes it clear he considers Varan the lackey of the Overlords. They argue over the status of the Mutts. Varan considers them a disease to be weeded out. Ky believes it murder of his people. The argument escalates. Ky accuses the Overlords of polluting his world and enslaving his people. Varan and he nearly come to blows.
The fracas is prevented only when the group is shepherded to Decontamination (save Varan, who is sent to see the Marshal). Only one guard and one Solonian, Varan’s bodyguard, remain in the Trans-mat lobby. The guard notices the Solonian is hiding his hand. Grabbing the limb, the guard sees it is green and scaled. He screams for help, only to be killed by the mutated Solonian.
In their private conference, Varan is furious with the Marshal that Ky has been allowed to attend the conference. Wiser than his native representative, the Marshal insists that Ky not become a martyr. He has a plan for Ky and needs a trustworthy Solonian from Varan…
The Doctor uses his sonic screwdriver to burn out the lock on the cupboard doors, breaking and entering into Skybase One. This intrusion is detected by a communications operator and a klaxon whines. “Attention. Attention. Computer confirms door malfunction in storage area four.” Jo responds, “That’s us.” The Doctor replies, “Yes, I know. I’m not sure I like being described as a malfunction.”
Two guards, Stubbs and Cotton, are in the middle of a chess game during their break. Responsible for checking the status of the base, Stubbs thinks they should deal with the door malfunction, but Cotton talks him out of it, reasoning that they just got back from a “Mutt” hunt and should put it off until morning. Cotton also mentions that their superior, “His Nibs”, the Marshal, won’t be “rushing about tonight”.
The Marshal explains to Varan that he needs someone completely trustworthy under his wing. Varan assures him all his warriors are loyal to him and will fight to the death if he orders so. Satisfied, the Marshall gives him a pass. Varan approves of it, but the Marshal is concerned Ky won’t be as enthused about accepting a handout from a human, and sends him off with the request that he will want to see the dependable Solonian man he offered to recruit. When Varan has exit the Marshal’s office, his true, duplicitous nature shines through in a moment of solitude. The Marshal takes a moment to recognize how gullible Varan was, muttering to himself, “The fool.”
As they explore the Skybase and venture deeper into the corridors, the Doctor and Jo find nobody around. The Doctor calls out, hoping to get a reply. When that merits no answer, they wander into Storage area 3. The Doctor tries to open a closed door panel, but it remains shut. He pulls out his sonic screwdriver again and begins disabling the lock again. Just as he remarks that they “can’t wander around all night without nobody noticing”, they are attacked by the mutated Solonian bodyguard. Jo spots him moments before the Doctor cracks the door lock. The door shuts on the bodyguard’s arm and traps him in place. The Doctor tries to prevent him from forcing his way out by holding the door hatch closed.
A second warning is issued by the comm operator. Instead of a passive notification, this one is an urgent warning demanding action at once. “Attention. Attention. Door malfunction in storage area three. Immediate investigation ordered. Possible emergency. Out.” Stubbs and Cotton are dispatched to investigate the door’s failure, no longer given the leniency to shirk off their duties. Stubbs instantly regrets listening to Cotton when they should have gone to investigate the first malfunction and how much trouble this bungle has caused them. Finding the Doctor and Jo under attack, they order them to get away from the door. The Doctor protests that doing so is foolish because the man who attacked them could quickly overpower them with his mutated hand. Cotton has little other choice but to shove the non-compliant Doctor and Jo away from the door. Once the bodyguard charges through, Stubbs doesn’t hesitate to shoot him, killing the Solonian. He delivers a report into his communicator that he and Cotton have investigated the storage malfunction, coming into contact with a mutant native and destroying it. He also declares that they have found two “non-personnel” in a restricted area, which will now be held, presumably until they are identified. Casual at performing his job, Stubbs is friendly enough to greet the Doctor and politely asks him and Jo if they will please come with them to reception. The Doctor surmises they don’t have a choice to refuse and have to follow the guards. Stubbs and Cotton take the Doctor and Jo into custody. The Doctor questions Stubbs about reporting a mutant native, and Stubbs confirms this is right. The slain Solonian can be seen with ridges protruding down his back along with the mutated arm.
With Varan’s bodyguard dead and two trespassers found, the Marshal is being dressed down by his superior, an Administrator from Earth. The Administrator has a bombshell to be dropped at the conference. The Empire is pulling out of Solos. Earth is near economic, political and environmental collapse. An empire is a luxury they can not afford at this point. The Marshal is livid. He believes this to be all the more reason their colonization of Solos is imperative. The Administrator scoffs. It would require genocide of the already mistreated Solonians. The decision has been made. Ky will be getting all he demands. As the Administrator leaves the room, the Marshal summons Varan again.
After waiting in the reception room overnight, the Doctor and Jo await the arrival of officials. Wearing sunglasses, Jo peers out through a porthole and remarks that they can now see the planet Solos in daylight, but is dismayed by how “grey and misty” it is compared to Earth. The Doctor regretfully informs her that there is no difference in forethought. This is a time period where the people are used to the crumbling thirtieth century Earth empire, by which time the people of Earth have tarnished the beauty of the once blue planet with over-industrialization, making even more grey and misty than Solos. He describes 30th century Earth as “Land and sea alike, all grey. Grey cities linked by grey highways across grey deserts.” Jo is appalled to learn this. The Doctor grimly reminds her how humanity can go too far with its exploits. “Slag, ash, clinker. The fruits of technology, Jo.”
Before heading to the conference, the Marshal and Administrator stop to interrogate Jo and the Doctor. However, the Doctor has had time to submit statements which explain their intentions for coming to Skybase One, tactfully leaving out the part that they arrived from an entirely different time period. The Doctor says they came to the Skybase from Earth, sent by Overlord Centre. The Administrator sees the Doctor is referring to the council on Earth, but is confused by their arrival because the council’s interest in Solos has ended. Spinning a yarn, the Doctor has him think the council thought otherwise when they sent him and Jo up to the Skybase. The Marshal, an insidious man at heart, is quick to suspect them out of paranoia that his underhanded dealings have been caught, and these two strangers threatening to expose him as a crook. The Administrator is more sanguine. He tries to allow the Doctor to speak and be reasonable in the company of an evidently perturbed and vocal Marshal, but to no avail. The Marshal drills the Doctor with questions about his departure time. When the Doctor gives him a hazy reply, the Marshal is convinced he’s lying altogether, more so because he lacks a clearance pass. When the Doctor argues why it is important he knows how they got to the Skybase, the Marshal browbeats him and concludes he and Jo are from Solos.
Exasperated, the Doctor reasons with him that they had a mission to give someone on board Skybase One a container by presenting both the Marshal and the Administrator with it. However, it refuses to unlock for anyone. Since it will only open for the person it is meant for, neither of them are supposed to possess it. The Doctor is unable to prove it is safe because he cannot open it, either. The Administrator perceives the offering of the sealed box as a joke, and the Marshal believes it can be opened with force. He snatches Stubbs’s gun and attacks the container, shooting it twice. It huffs with smoke from the laser impacts without even leaving a scratch on it. Infuriated, the Marshall thinks it is the handiwork of saboteurs in league with the Mutts. Annoyed, the Doctor snips, “Oh, don’t be a fool. If we were saboteurs, that’d be a bomb, and thanks to you we’d all be blown to smithereens by now.” Jo also comes to the Doctor’s defense when the Marshal is skeptical they’re being truthful about their mission, but it still doesn’t get through to him. After touting multiple wild accusations toward the Doctor and Jo, the Marshal’s innate fear of being caught finally causes a slip of the tongue. In an irrational blurt, he believes them spies from Earth, special agents from the council sent to check up on him.
Cotton enters, telling the officials the Solonian delegates are ready to see them. The Doctor tries to have the Marshal take the box with them in case the person who is intended to have it is present at the conference. Stubborn and snide, the Marshal dismissively says there are “far more important things” to be dealt with than a simple box or two suspicious occupants of Skybase One. Whoever they are, they can wait until after the conference with the Solonians. Regardless, he leaves Stubbs posted with the Doctor and Jo and makes it clear he doesn’t want them to leave Stubbs’s sight, not willing to turn a blind eye at the unwelcome pair on his base.
As the representatives of Solos assemble, the Marshal passes a small device to Varan. Varan passes it to his son.
The conference is being telecast throughout the Skybase. The Administrator begins his speech to the Solonians. Watching the telecast together, the Doctor uses the distraction to overpower Stubbs and make his way to the conference with the message pod.
The Administrator’s speech, though intended as conciliatory, comes off as condescending and bombastic. Ky disrupts it several times. As they shout at each other, Varan’s son shoots a dart from the device. It strikes the Administrator in the neck. He drops dead. The conference erupts into chaos. The Marshal orders Ky’s arrest. He flees the conference chamber, nearly colliding with the Doctor just outside the door. The momentary contact has an immediate effect on the message pod; it begins to open for Ky, its intended recipient.
Despite the Doctor’s protestations, Ky grabs Jo as a human shield and continues to run. He pulls her into the Trans-mat as the Marshal orders his men to open fire. Their blasters turn the Trans-mat into a shower of sparks…
The smoke clears. The Trans-mat chamber is empty. The Marshal points out Jo’s safety may be short lived. She has no oxymask, nor shall she long survive on Solos without one.
At the Trans-mat’s ground station, Ky and Jo materialize amidst klaxons. Dodging fire from the ground station’s lone guard, they escape through an airlock onto the polluted world. They are pursued by more troops, but this is to their advantage. Ky overpowers one and takes his oxymask.
High above in the Skybase, the Marshal has assumed command in the wake of the Administrator’s death. He strikes a bargain with the Doctor — open the message pod and the Marshal’s men will try to save Jo. The Doctor agrees reluctantly. He is escorted to the Skybase’s lab. The Marshal assigns his own scientist, Jaeger, to assist. Jaeger is put out by the distraction from his own work on the Solonian atmosphere, but complies.
The Marshal turns to the loose ends of the assassination. He kills Varan’s son with the dart-gun and tries to do the same to Varan himself. Varan escapes, but the Marshal declares him a Mutt and orders him captured and executed.
With Jaeger’s reluctant help, the Doctor builds a particle reversal device to see the contents of the message pod. Stunned when the process works, Jaeger realizes that particle reversal could convert the Solonian atmosphere to a more habitable one in days.
Seeking shelter in a cave, Ky explains his people’s suffering to Jo. Meanwhile, Stubbs is joined by the Doctor in the search for Varan. They think they have him cornered, but Varan disarms Stubbs and nearly kills him. The Doctor’s crack shot with a blaster takes the blade out of Varan’s hand.
Having learned the truth about the assassination from Varan, Stubbs is now the Doctor’s ally, albeit clandestinely. They lie to the Marshal, claiming Varan is dead. The Marshal, meanwhile, has coaxed Cotton into lying also, corroborating the Marshal’s claim that Jo has been found and is in a hospital on Solos.
Their deceptions at an impasse, the Marshal shuffles the Doctor off to Jaeger’s project to alter Solos’ atmosphere. Jaeger uses the Doctor’s outrage at the proposed method — rockets launched into the atmosphere, killing all the Solonians as a “side effect” — to manipulate him into offering his particle reversal method as alternative.
Cotton speaks to the Doctor discreetly. He explains that Stubbs has brought him in on their side and tells him the truth about Jo. The Doctor and Cotton devise a method to get the Doctor off the Skybase. Then the Doctor turns the tables on Jaeger, using his enthusiasm for particle reversal to make him a patsy for the escape.
Stubbs informs Varan of the plan to get off the Skybase. Though suspicious, he appears to agree. The Doctor overloads the Skybase power, stunning Jaeger. He makes his way to the Trans-mat, only to be grabbed by Varan. With his blade at the Doctor’s throat, he growls, “Die, overlord!”
With Varan literally at his throat, the Doctor trans-mats to Solos. As the two emerge from the trans-mat chamber, the Doctor incapacitates his assailant with some Venusian aikido. He extracts Varan’s word as a warrior that he will take the Doctor to Ky. Despite the onset of a firestorm in the sky (a “side effect” of the Marshal’s manipulation of the atmosphere), they set out into the Solonian night. Elsewhere on Solos, Ky and Jo watch the same firestorm before a group of agitated Mutts forces them to retreat deeper into the cave.
After expressing his frustration with Jaeger by means of a cathartic yelling session, the Marshal orders his scientist to go ahead with the original, more genocidal atmosphere modification plan. He summons Stubbs and Cotton to his office. They are understandably apprehensive, what with their recent treason. They are dressed down, but the Marshal does not consider them traitors, merely incompetent. He sends them down to Solos to pursue the escaped Doctor and Varan, flushing them out of the caves with gas grenades.
Varan’s tracking leads them to Ky and Jo’s fire. Despite Varan’s protests that he will go no further, the two proceed deeper into the cave after their quarry. Ky, meanwhile, fends off a mob of increasingly agitated Mutts. The Doctor and Varan’s arrival helps quell the beastly melee, but Jo has run deeper into the caves. She finds a chamber of light and sound, driving her to unconsciousness. A figure in a protective suit emerges and moves to her side.
The Doctor finally gives the message pod to Ky. In his hands, the pod opens, revealing a set of stone tablets. Varan and Ky, expecting weapons, are disappointed. Ky identifies the markings on the tablets as ancient Solonian writing; no one understands it anymore, as the Overlords have destroyed their culture. Varan storms off, declaring he shall lead his village against their human oppressors. Ky and the Doctor, meanwhile, begin searching for Jo.
The Marshal begins deploying his gas bombs. He sends Stubbs and Cotton deeper into the caves after the Doctor. Monitoring them on his radio, the Marshal overhears their friendly greeting to the Doctor, then sets off an explosive to seal them in.
Varan returns to his village. It is deserted save for an elderly Solonian in the midst of transforming into a Mutt. He is horrified to see the beginnings of the transformation on his own arm, then hears a voice in his head, telling him to “go to the place of sleeping and light.”
The figure in the protective suit emerges again. It gestures for the Doctor and his entourage to follow. It leads them to a lead-lined chamber deep in the caves. “Professor Sondergaard, I presume,” quips the Doctor.
While the Marshal orders his men to continue sealing the caves, Sondergaard says Jo wandered into a chamber of intense radioactivity. He believes that while there are normal changes in the ecosystem as the five-hundred-year seasons change, Jaeger’s experiments altered the natural balance.
The Marshal returns to the Skybase and orders Jaeger to begin the bombardment of Solos with ionization rockets to change its atmosphere. Below, Ky opens the pod again to display the tablets. Sondergaard tries to translate them. He declares them the Solonian equivalent of the Book of Genesis, but his attempts to scry meaning from them are interrupted by the cave’s continued collapse. Ky, Jo, Stubbs and Cotton head out to the relative safety of Varan’s village, while the Doctor and Sondergaard remain to continue the study of the tablets.
The Doctor hits upon the meaning of the tablets – a calendar of the five-hundred-year Solonian seasons – and interprets one symbol as referring to the radiation of the chamber. Sondergaard and he set off to explore further.
Varan addresses his few remaining warriors. He is interrupted by a report of the approach of Overlords. When Stubbs, Cotton, Ky and Jo arrive, they are ambushed and forced to surrender their guns. Varan declares his plan for revenge, to attack Skybase using his captives as hostages and shields.
As they plunge deeper into the radioactive chamber, the Doctor is forced to leave Sondergaard when the radiation overwhelms his suit. At the heart of the chamber, the Doctor finds a glowing statue with a green crystal set in it, which he pockets. He retrieves Sondergaard and leaves the chamber.
Aboard Skybase, the Marshal’s plan is forced to accelerate. An Earth Empire Investigator will be arriving shortly. Unbeknownst to him, Varan has already taken a trans-mat ground station and is beaming aboard.
The Doctor tries to analyse the crystal he retrieved, but Sondergaard’s equipment is too primitive. They, too, set out for Skybase.
The launch of the ionization rockets is imminent, but momentarily interrupted when Varan’s incursion is detected. The Marshal orders the countdown to continue while he assembles a squad to repel the intruders. They ambush Varan’s warriors, slaughtering them with superior weaponry. The Marshal personally dispatches Varan. Unfortunately, his blaster fire tears a hole in the Skybase’s hull, blowing Varan out into the vacuum.
As the ionization rockets launch, the Marshal, Ky, Stubbs, Cotton and Jo all cling for their lives as the air rushes out into space…
Jo, Ky, Stubbs and Cotton struggle out of the depressurized chamber. They find themselves arrested by the Marshal and facing summary execution. The firing squad takes aim, only to be stopped at the last moment by an irate Jaeger. Unconcerned with the welfare of the Marshal’s captives, Jaeger is livid that his rocket barrage was a complete failure. Due to poor maintenance and the Marshal’s unreasonable timetable, the rockets poisoned Solos’ surface rather than ionizing its atmosphere.
Jaeger mentions the Investigator in passing and Stubbs and Jo drive home the point. Even with them executed, the Marshal’s men are tired and want to go home. One of them will report the true state of the Solonian occupation. The Marshal seems unconcerned. If necessary, he will blow the Investigator’s ship out of space. Jo bluffs the Marshal, claiming that the Doctor is the Investigator’s advance party.
On the planet below, the Doctor and Sondergaard find the bombardment waning, but the damage done. The plant life is already contaminated by the ionization crystals. Sondergaard is too weak to continue, but insists the Doctor go to Skybase, to solve the mystery of the green stone.
The Marshal returns to Solos, to capture the Doctor personally. He hopes that, with Jo a hostage, he can persuade the Doctor to use his particle reversal techniques to clean up the environmental mess on Solos before the Investigator arrives. The troops track the Doctor through the mist, but he overpowers one and flees to the trans-mat ground station.
The chase continues onto Skybase, where the Doctor finds his captive friends. He is about to release their handcuffs with his sonic screwdriver when the Marshal steps out, springing the trap. He blackmails the Doctor into cooperating.
The Doctor outlines his plan to Jaeger: use the trans-mat’s macrophaser to effect particle reversal in swaths across Solos. This will, of course, necessitate shutdown of the trans-mat system.
Jo slips out of her cuffs and disarms the guard. Cotton tries to contact the Investigator’s ship, but guards are already at the door. Luckily, Stubbs holds them off. They are unwilling to fire on one of their own. The Marshal arrives and demonstrates no such hesitation. He sprays the room with blaster fire. Even as the Investigator is contacted, Stubbs is gunned down. Leaving his fallen friend behind, Cotton leads Jo and Ky to an escape: the tranmat. They enter the trans-mat, only to find it offline; the Doctor’s procedure has just begun.
Sondergaard has returned to the cave. He is nearly accosted by a guard, only to be saved by a Mutt. Mutts have gathered. Sondergaard explains what he has learned. They have one chance: the Doctor.
Far above, the Doctor and Jaeger begin sweeping their particle reversal beam across the planet. It undoes the damage of the rockets, but the Marshal is not satisfied. He threatens Jo if the Doctor does not terraform the planet further. Just then, the Investigator’s ship approaches Skybase.
Jo, Cotton and Ky are kept as hostages to ensure the Doctor does not expose him to the Investigator. Cotton realizes that the Marshal has ordered them held in the thaesium storage chamber, a chamber that will be flooded with radioactivity as soon as the Investigator’s ship refuels.
Outside Skybase, the ship slowly moves to dock…
The Investigator arrives, immediately suspends all troops loyal to the Marhsal and begins his inquiry. With Jo in his grasp, the Marshal has an unwilling ally in the Doctor.
The fuel probe from the docked ship enters the thaesium chamber. Jo, Ky and Cotton climb in, hoping to escape the radiation in the ship. They make their way to the inquiry. With Jo safe, the Doctor speaks freely. He accuses the Marshal of genocide. The Marshal erupts with rage, sputtering that the Mutts should be wiped off the face of the planet, which persuades the Investigator.
However, the Investigator is obligated to due process and insists on proof of the Doctor’s claims about the Solonian mutation. Sondergaard arrives on Skybase and tries to corroborate the Doctor’s claim. He is followed by a Mutt, whose presence throws the proceedings into chaos. In the brouhaha, the Marshal grabs a blaster and guns down the terrified Mutt. The violence persuades the Investigator to reinstate the Marshal’s command.
While the Doctor, Sondergaard and Jo flee, Cotton attends to Ky, who has been ill since their experience in the refueling chamber. He pays for his compassion. The Marshal orders Cotton and Ky thrown back in the refueling chamber, despite the thaesium radiation being at a lethal intensity.
The Doctor seals himself in the lab. Sondergaard and he try to analyse the green stone. They put it under the particle reversal machine and realize it must be the catalyst that allows the thaesium radiation to bring the Solonians to their next stage.
The Marshal blasts his way in. He orders Jo and Sondergaard thrown in the radiation chamber with Ky and Cotton. He does not know this is exactly what the Doctor wishes. With the combination of the stone, the radiation and Ky, the mutation should succeed this time. The Marshal keeps the Doctor in the lab to complete the terraforming.
Sondergaard gives Ky the stone and the Solonian begins to change into a Mutt, faster than any of the previous transformations.
The Doctor continues to work under the watch of Jaeger and the Marshal, but uses the distraction of the Investigator bursting in to switch a pair of wires in the particle reversal device. The Investigator has learned he is now the Marshal’s prisoner. The Marshal intends to transform Solos into a “New Earth” and make the Investigator’s crew his first batch of settlers. The Doctor points out that he said the Marshal was quite mad.
Ky’s transformation completes. He emerges from the larval Mutt stage as a glowing, telepathic and almost omnipotent being. He thanks Sondergaard for his help and disappears, opening the door almost as an afterthought. The now godlike Ky floats through the corridors of Skybase. The guards he passes fall dead as he goes.
In the lab, Jaeger throws the switch on the Doctor’s device, only to be killed in the blast as his sabotage does its work. The Marshal trains his gun on the Doctor, but Ky appears and vaporizes the Marshal in retribution for his torture of the Solonians. Ky thanks the Doctor and vanishes.
With Sondergaard staying on to help the Mutts complete their transformation and Cotton appointed to oversee the withdrawal of the Skybase to Earth, the Investigator wants the Doctor to return to Hyperion and give a full account of his involvement with the Solonian affairs. Aware that he is a complete, unqualified stranger masquerading as an official, the Doctor makes an excuse to leave by saying that Jo doesn’t look so well, and Jo catches the hint. The Doctor and Jo head back to the TARDIS before the Investigator can learn he’s a phony. With a terrible pun, the Doctor returns to his blue box in the broom cupboard, breaking out the same way he broke into Skybase One- using the sonic screwdriver on the door controls. As the TARDIS departs, a familiar alert on the comm speaker brings their adventure full circle. “Attention! Attention! Computer confirms malfunction in storage area four. Investigate, please. Investigate, please.”