In a small Welsh village, a man is stumbling through an abandoned mine. His face is filled with terror at some unseen danger. The only hint is the evil-looking green gas that curls at his feet.
On the surface, a businessman named Stevens drives up to a factory in a white car. The factory gate is surrounded by disgruntled men. His colleague Elgin greets him and tells him the men are nervous about the future. Stevens addresses the miners, telling them the paper he holds will make them wealthy.
But even as he reassures them, the miner has found the lift and begins his ascent to the surface. We can now see the source of his fear -- his hand is glowing bright green.
Stevens is making progress with the miners. He tells them at coal is dead -- their future lies with the oil produced by Global Chemicals. They now have permission to expand the plant -- which will mean more good-paying jobs . . . better houses . . . better cars . . . But a long-haired young man interrupts that it will mean more muck, more death and more devasatation. Elgin explains that the man is Professor Cliff Jones -- a troublemaker who is very popular in the press. Stevens responds to Jones, accusing him of resisting progress. But the young man replies that Stevens just wants more profits for Global Chemicals at the expense of people's health and the environment. The miners are unreceptive to Jones -- they need jobs. But Stevens calms them down. He explains that his company is of course concerned with the environment. But his reconciliation is interrupted by a loud whistle. The miners recognize it as the pit alarm. They rush to the mine. But the man has died. He is slumped over the whistle, his body now completely green.
At Unit HQ, Jo Grant is enjoying a light lunch in the lab when the Doctor emerges from the TARDIS, carrying a circuit. He explains that it is the worn-out space-time coordinate programmer. Jo jokes that it's no wonder they never got to Metabilis Three. As the Doctor continues to tinker, she picks up the paper. The two then go off on conversational tangents as the Doctor talks of Metabilis Three while Jo reads aloud the story about Global Chemicals with growing alarm. She dashes out of the lab to pack for a trip to Llanfairfach. The Doctor, oblivious, thinks she is packing for Metabilis Three but is quicky disillusioned. In Llanfairfach, Jones and the miners examine the dead man. He was in the mine for a routine inspection. Jones is puzzled, unable to figure out what might have happened to kill the man in such an extraordinary fashion.
The Brigadier, alerted to the situation, asks the Doctor to help with the investigation. But the Doctor is resistant, eager to head to Metabilis Three. The Brigadier tells him that UNIT has a duty to protect Global Chemicals. Just then, Jo returns and the Brigadier asks her to join him. But Jo is furious that the Brig is going there to help the oil company. The Doctor asks if she's ready to go the Metabilis Three by she insists she needs to help stop Global Chemicals. The Brigadier is puzzled, convinced that the country could use more oil and that Professor Jones is a crank. Jo replies that she will support Jones even if it means quitting UNIT. But the Brigadier is conciliatory, offering her a ride to the Welsh village.
After he leaves, the Doctor tries to convince Jo to go to Metabilis Three with him. But Jo insist that she wants to go help Professor Jones, commenting that he reminds her of a younger version of the Doctor. He is bemused, not knowing whether to be flattered or insulted. But he tells her to go ahead and tell the Brigadier he will join them later. Jo is obviously disappointed. After she leaves, the Doctor quietly muses that she is growing up. He then strides into the TARDIS and dematerializes.
The Brigadier and Jo arrive in Llanfairfach and ask a milkman for directions to Global Chemicals. When Jo asks him where Professor Jones' Wholeweal Community is, he also provides directions to "the Nuthatch". The Brigadier drives up to a farm, decorated with "Wholeweal" painted in bright psychadelic colors. A nervous Jo walks in, letting the Brigadier continue on to Global Chemicals.
On the other side of the Galaxy, the TARDIS materializes on a blue planet. the Doctor steps out cautiously as strange animal noises greet him. He looks around and gazes at the blue sky -- he has at least reached Metablis Three! But he has little time to enjoy the view as he is immediately attacked by an unseen creatures.
Jo walks into Jones' commune, carrying a bulky suitcase and wearing a big fur-lined coat. She sees a sign advertising a room but can't find anyone. Finally, she stumbles upon a lab where Professor Jones is hard at work. He informs her that everyone else is working in the fields.
He then notices the open door and yells that she's ruined his experiment. She stumbles around the lab and tries to explain her presence, telling her that Nancy said she could come down. Professor Jones resumes his work, saying he wasn't told about Jo. Not having realized who she's talking to, she tells him she's come to see Professor Jones, then promptly knocks some equipment off a table. A frustrated Jones pushes her into a chair and tells her to sit still. He calls her a kid but seems friendly in a gruff way -- very much like the Doctor at their first meeting. With a glint in his eye, he welcomes her to the Nuthatch.
As for the Doctor, he is frantically running around Metabilis Three, dodging the amazingly aggressive fauna.
Jones works silently for a while before asking Jo what she knows about entemology -- particularly if she can identify a certain insect that is crawling up her leg. She jumps up with a scream and Jones laughs. He tells her he just couldn't stand the silence any longer.
The Doctor is now wading through snow on Metablis Three.
Jo asks why Jones is growing mushrooms. He tells her it is a fungus that he hopes will replace meat. The Nuthatch isn't just a commune -- it's a full scientific laboratory. She asks if Professor Jones thought of that and then realizes with a start that she is, in fact, talking to the very Cliff Jones she came to see. She's miffed for a moment but then grins. It's clear that she find the man to be oddly charming.
Stevens is confronting the Brigadier, explaining that a lot of money has been invested in his project. But the Brigadier is unmoved. He is determined to investigate the matter of the green man. His first step will be to call his errant scientific advisor.
The Doctor is, however, not within light years of a phone. He is crawling on his hands and knees as the phone in his office begins to ring. The Doctor finally reaches the top of a mountain. A huge bird swoops at him but he ducks and grabs a blue crystal.
The Brigadier tells the operator to keep ringing the Doctor until he answers. He then asks Stevens why Professor Jones is opposed to Global Chemicals. Stevens can't imagine why as they are conserving resources -- getting more useable fuel out of oil.
Jones, meanwhile, is explaining to Jo that the Global Chemical process still pollutes and it will still mean Britain is dependent on oil. He tells her that the Nuthatch is powered by wind and the river.
Stevens tells the Brigadier there is no waste or pollution from the oil refinery. The Brigadier is skeptical but Elgin assures him that it's true.
Jones tells Jo that the Stevens Process must be based on polymerization, which would produce a highly toxic sludge. He wonders what they are doing with it and how it might be connected with recent events. Jo speculates that they are pumping the waste into the mine. She thinks they should take a look but Cliff is strangely uninterested. Jo accuses him of patronizing her and leaves in a huff, with Cliff reminding her to close the door on her way out.
At the mine, a man named Dai Evans is puzzled by the death of his friend and decides to investigate the mine.
Stevens tells the Brigadier that no one should go down into the mine and it should be sealed. But the Brigadier is determined to carry on with his investigation -- as soon as the Doctor arrives.
The Doctor hurries back into the TARDIS and takes off as stones and spear are thrown at him. The phone continues to ring in his office as the TARDIS returns. The Doctor stumbles out and answers. He agree to go to Llanfairfach and quickly drives off in Bessie.
Dai enters the lift and descends into the darkness of the mine.
The Doctor arrives at the refinery and the Brigadier leaves Stevens to meet with him. Stevens is upset that the Brig wants to investigate the mine and calls for Hinks. A burly thug enters and Stevens, suddenly disoriented, tells him that no one is to enter the mine. Hinks nods and leaves. Stevens then takes out a strange headset, plugs it into the wall and puts it on. He closes his eyes, clearly comforted by the device.
Jo arrives at the mine head. She tells the two men at the top of the shaft that she's with UNIT and needs to go into the mine. But an alarm suddenly rings out. It's Dai calling for help -- his hand is glowing bright green! Bert wants to go down and Jo insists on going with him, telling him she knows first aide.
The Doctor and Brigadier roll up to the mine in Bessie. They don't notice Hinks slinking around in the shadows. Bert and Jo climb into the lift and Dave sends it down. The Brigadier sees the wheels spinning and realizes someone is using the lift. They rush in and tell Dave to stop the car. He pulls some levers but nothing happens. Bert and Jo grab onto the car as it plunges helplessly toward the bottom of the mine.
Jo and Bert are descending into a Welsh mine to investigate the mysterious events connected with Global Chemicals. But the Doctor and the Brigadier are trying to stop them. The Doctor pulls frantically at the lift controls to stop it but the lift plunges into the darkness, out of control.
The Doctor, thinking quickly, jams the spinning gears and tells Dave to reverse the motor, even it destroys the machine. He hesitates and the Brigadier steps in, halting the lift. The lift grinds to a halt as explosions rip through the motor. The lift has finally stopped -- but the depth gauge reads 600 yards out of 600 yards.
Jo and Bert struggle to consciousness. Bert opens the car and drops a tool. It clangs to the bottom of the shaft less than 20 feet below them. He begins to worry that the cable -- strained from the descent -- will give out. He and Jo decide to get out of the car and lower a rope to the bottom of the shaft.
Dave tells the Doctor that lift drive is broken beyond repair. And they can't use the other lift since they are linked. The Doctor suggests a repair that would make it possible to use the other lift -- but it would require heavy cutting equipment. Only Global Chemicals would have such equipment.
Almost 2000 feet below them, Jo and Bert have climbed down to the base of the shaft. They try to call up to the surface but the line is broken. They then find Dai, moaning and glowing bright green.
Elgin takes the phone call from the Brigadier and agrees to loan the the cutting equipment. But he is cut off by Stevens. Dave then remembers that Wholeweal borrowed the equipment and the Brigadier calls them. Jones answers the phone at the Nuthatch. He tells the Brgaider they don't have the equipment but then rushes to the mine, evidently concerned about Jo.
Stevens tells his associate Fell to inform the Brigadier that they don't have any cutting equipment. At first, Fell objects -- it would be murder to abandon Jo and Bert. But Stevens insists that the mine can not be explored. Fell tries to leave but is blocked by Hinks. Suddenly, an electronic voice rings out. It tells Stevens to "process" Fell. Fell asks whose voice that was. Stevens cryptically responds that it is "our boss". Fell will understand soon.
Dai Evans is fading fast at the bottom of the mine. Jo and Bert worry that whatever has hurt him is still there.
Fell enters Stevens' office, where the Brigadier is trying to obtain cutting equipment. Fell tells them they have nothing that could be used to cut the cable. But he acts strange -- robotic and unfeeling. As Stevens and the Brigadier leave, Elgin tries to talk to Fell about the equipment. But the latter is unresponsive.
The Brigadier quickly places a call to Mike Yates while Jo and Bert try to stay calm at the bottom of the mine. Meanwhile, the Doctor shows Dave and Cliff Jones a pin removed from the brake linkage. The lift must have been sabotaged.
Jo and Bert are now desperate to help Dai. Bert remembers that there might be another exit used in a previous accident in the mine. They decide to try their luck and move off into the darkness.
The Brig returns to the mine and tells the Doctor that Global Chemicals doesn't have any cutting equipment. The Doctor doesn't believe it and Cliff remembers that the Nuthatch borrowed it only recently -- it's in a shed on the Global Chemicals compound. The Doctor is finally introduced to Jones and says he is honored to meet him. Jones suggests stealing the equipment from Global Chemicals but the Brigadier is opposed. As he leaves to go to the nearest city for cutting equipment, the Doctor and Jones decide to go to Global Chemicals anyway.
Sometime later, Jones and the Nuthatch inhabitants show up banging drums and marching to protest against Global Chemicals. As the security guards go to watch, the Doctor sneaks in with the help of a crane. But the cameras pick him up as he follows Professor Jones' map. Stevens and the boss decide to capture him. A voice rings out, telling the Doctor to stop. Then security guards come to arrest him. The Doctor quickly knocks out all three of them and runs for it. But more guards swarm toward him and he is eventually trapped by Stevens. Stevens explains that the cutting equipment isn't there and opens the shed to show that it is empty. But Elgin looks skeptical.
Jo and Bert continue to hurry through to mine. The air is getting stuffy as they struggle to escape.
The Brigadier suddenly drives up to the mine with an acetylene torch. He found it by coincidence at a petrol station. They decide that the Doctor, Dave and two other miners will go down after Bert and Jo.
The two youngsters have reached a stopping point in their journey out. They turn off their lamps as they rest. But they see a green glow around them. They head toward it and smell something rotten. Finally, they see some green ooze coming out of the rock. Bert unwisely touches it.
The Doctor and the miners reach the bottom of the shaft. Dai is dead, his body completely green. The Doctor calls out to Jo but then finds a note from her. They head out after the two young people.
Jo is trying to drag Bert so safety but he is weakening. His fingers are now glowing green and he's scared he's going to end up like Dai. He tells Jo to leave him and get help.
The Doctor and Dave find the green light, the rotten sell and the ooze. And they find Bert, who is fading fast. The Doctor tells Dave to take Bert to the surface while he goes after Jo.
Jo rounds a corner and stops in shock. She is facing a cave filled with green maggots wriggling in green muck. The Doctor finally catches up with her but the cave suddenly collapses, trapping them. Maggots slither out of the rubble, advancing steadily on the Doctor and Jo!
The Doctor and Jo have finally located the source of the mysterious green illness that is infecting the miners in Llanfairfach. A lake of green slime filled with wriggling green maggots. But the cave collapses behind them and green maggots advance on them out of the rubble. They are trapped!
The Doctor remains calm, telling Jo they will be fine as long as they avoid contact. They find an old mine car and mount it on the tracks.
On the surface Bert is being taken to the hospital -- dying from his contact with the green slime. Jones tries to reassure Dave. He now believes that Global Chemicals is responsible. He wants to go down into the mine to help Jo and the Doctor but the Brigadier stops him. The Brig tells Jones that he is just as worried but has confidence that the Doctor can handle anything. He does, however, agree to make another call on Global Chemicals.
Down in the mine, the Doctor and Jo fish wooden poles out the rubble. They then punt the mining car across the green swamp toward safety.
Elgin informs Fell that survivors have been brought out of the mine, but his colleague is unmoved. Elgin pushes him, asking about the cutting equipment and the mine. Fell seems about to talk but then hurries away. He enters a pumping room, followed by Elgin.
The Doctor and Jo finally complete their journey across the disgusting green swamp. They gratefully exit the mine car and continue their journey out of the mine.
The Brigadier is telling Stevens that UNIT will be arriving to deal with the situation and investigate the problems. Stevens is opposed and they argue. Then Stevens smirkingly warns the Brigadier to be more prudent, implying he has friends in high places. The Brigadier tells Stevens that he has friends on the cabinet. Stevens responds by picking up the phone and dialing the Minister of Ecology.
The Doctor and Jo scramble up the mine. They find some huge green eggs and the Doctor, intrigued, picks one up.
Elgin approaches Fell in the pump room. Fell tries to get him to leave but Elgin stays, peppering the evasive Fell with questions.
The Minister of Ecology talks to the Brigadier. He opposes any investigation -- UNIT should be helping Global Chemicals. The Brigadier tries to argue but the Minister simply hands the phone to the Prime Minister, who orders the Brigadier to help Global Chemicals. Stevens does indeed have friends in high places!
The Doctor and Jo finally reach the end of the tunnel only to find a corrugated pipe. Quickly, they begin to climb. But this sets of an alarm in the pump room. Elgin and Fell see the Doctor and Jo on the monitor. Fell is preparing to pump waste into the pipe, which appalls Elgin.
The pipe starts vibrating and the Doctor and Jo hurry to get out. Elgin tries to argue with Fell, who is growing more and more confused. As the Doctor and Jo bang at the window of the hatch, Fell finally tells Elgin how to open it. The Doctor and Jo are rescued from the pipe just in time to avoid the deluge of green waste.
Stevens tries to be conciliatory to the Brigadier. The soldier is cordial but clearly doesn't trust the businessman. But he reluctantly leaves to carry out his orders.
The Doctor is explaining about the maggots to Elgin while Fell quietly slides out of the door. But Jo is exhausted and the Doctor realizes he needs to get her to safety. But before he leaves, Elgin promises to help them.
Fell staggers into Stevens' office, utterly confused. Stevens helps him to a chair and puts a headset on him. Fell realizes that something has been done to his mind. The boss's voice sounds again. He tells Stevens that Fell is a failure and needs to be destroyed. Stevens reluctantly agrees and presses a red button. Fell leaves the room, rushes past the Doctor, Jo and Elgin, goes to a balcony railing and jumps to his death.
Stevens is visibly shaken by the event. But the boss only taunts him for being sentimental.
That night, at the Nuthatch, the Doctor is entertaining Jones' friends with stories of his adventures when he is interrupted by a phone call. As he leaves to answer, Jones informs Jo and the Brigadier that the "meat" they just ate was actually a fungus. He has a meat replacement but it is not perfect. He wants to go to the Amazon to hunt down a legendary fungus. He explains to the surprised Brigadier that everyone at the Nuthatch is a scientist working on windmills, ecology, sociology and a host of other problems. Jo is enthralled by Cliff, eager to hear about his trip to the Amazon.
The Doctor returns and tells them that Bert has died. Jo is crushed. The Doctor tells them that every cell in Bert's body had been attacked by the green slime.
Hinks tells Stevens about the egg the Doctor took. Stevens is concerned and tells him to retrieve it.
Jones comforts Jo for Bert. He tells her, "In the whole history of the world there's never been anybody just like Bert. And there will never be another even if the world lasts for a hundred million centuries." He kisses Jo on the forehead but before it can lead to anything else, the Doctor and the Brigadier return.
Jones and the Brigadier leave while the Doctor tells Jo to get some sleep. She wants to stay up and read Cliff's book about the Amazon. The Doctor tries to tell her about his trip to Metabilis Three but she seems uninterested.
Jones returns but the Doctor pointedly leads him off in a conversation, preventing any further "conversation" with Jo. The girl smiles strangely and then resume reading Cliff's book.
But even as Jo reads, the egg shatters and a green maggot emerges. It slithers hungrily around the Nuthatch until it sees Jo. It continues to advance quietly on her.
Jo is quietly reading a book in the Nuthatch when the green egg taken by the Doctor suddenly hatches. A loathsome maggot crawls out and approaches the girl, eager to feed.
But even as it approaches, another menace has entered the house -- the Global Chemical thug Hinks. He has entered the living room and sees it wriggling across the floor. He freezes and the maggot attacks, leaping on his neck. Jo turns and screams in horror. Cliff, the Doctor and the others arrives in a flash but the maggot has already disappeared. The Doctor realizes that the egg must have hatched. Nancy, one of the Nuthatch scientists, goes outside but is unable to find it. The Doctor scrapes up some of the slime for analysis.
In the morning, the Brigadier and UNIT are placing explosive charges in the mine, determined to close it off. A milkman drives by and is kept away. But he quickly guesses what they're up to.
Cliff is looking through a microscope at the green fungus, marveling at how rapidly it destroys human cells -- changing them to green slime like a virus. The Doctor thinks they need to get another maggot to examine. But Nancy interrupts them. The milkman has told her that UNIT is going to blow up the mine.
The Doctor hurries off to stop the Brigadier. The soldier needs to obey his orders but agrees to give the Doctor half an hour to persuade Stevens.
But the Global Chemicals director won't listen. The Doctor tries to explain that they can't observe the maggots and the eggs if the mine is blown up. Stevens just scoffs, calling the Doctor a crank who is just trying to stir up trouble. The Doctor accuses Stevens of trying to cover up what his waste is doing to creatures in the mine. But Stevens reminds the Doctor that he has emergency powers and can arrest the Doctor if he wants. He calls Elgin to bring in the man from the Ministry. A door opens and, to the Doctor's surprise, in walks Mike Yates!
As time runs out at the mine head, the Doctor tries to argue with Yates. But the undercover Captain insisted that he is just obeying orders while a confident Stevens looks on in silence.
Finally, time runs out. Over the protests of Jo and Cliff, Benton fires the explosives and the mine goes up in massive detonation. The explosion is heard even at Global Chemicals. The Doctor stomps out, appalled. Stevens warns him not to come back, then dismisses Yates.
The boss speaks up, mocking Stevens for enjoying the situation. The boss seems concerned and warns his "little superman" to be careful -- their day is fast approaching.
The Doctor asks the Brigadier what Yates is doing at Global Chemicals. The Brigadier replies that he doesn't trust Stevens at all and wanted a man on the inside. Still, he is convinced that the maggot problem has been solved. The Doctor and his friends aren't as sanguine.
Of course, they are right. Later that day, a cleaning lady is working in the pump room when she sees maggots squiggling around in the pipe. Benton and the soldiers are a the the maggots crawl out of the ground -- one killing a UNIT soldier.
Elgin, having been told of the maggots by the cleaning woman, goes to Stevens. Stevens dismisses the concern, telling Elgin to just flush more waste into the mine. Elgin refuses. He's going to blow the whistle. But before he can leave, Stevens locks the door and tells him to sit in the chair where Fell was programmed. Elgin resists but a strange sound rings out in the room and he walks to the chair in a daze. Stevens pulls out the headset.
Benton calls the Brig to report that maggots are now all over the pit. The Doctor begins to worry -- that maggot are a pupal stage -- what will they molt into?
UNIT tries shooting the maggots without success. Even armor-piercing rounds don't work. Other soldiers sprays pesticide on the maggots but they seem to feed on the stuff. The Doctor decides they need a biological weapon. Jones is working on a solution but needs more green slime. He doesn't want to risk getting a maggot.
The Brigadier calls Yates to see if the Captain can get him some of the oil waste. But Yates always has a Global Chemicals man at his elbow. The Doctor grabs the phone and tells Yates that he will break in to get some waste but Mike warns him that security has been doubled.
Just then the Doctor sees the milk truck drive up and gets an idea. Shortly afterward, he shows up at Global Chemical with a mustache, glasses and a funny voice pretending to be a substitute milk man. The guards let him in.
Jo is trying to talk to Cliff while he works on the green slime. It's clear they like each other, but Cliff is distracted by his work. Jo spills some brown fungus on Cliff's slides, infuriating him.
The Doctor sneaks into Global Chemicals. But once again, the alarm rings out and a voice tells the guards to arrest the milkman. The Doctor scurries into a closet and begins to change.
Jo tries to talk to Cliff but he is dismissive, sarcastically suggesting she make some tea. Frustrated, she scribbles a note and stomps out.
As Captain Yates and his guard are leaving for the day, they pass a cleaning woman. She turns to reveal the Doctor in a dress! Yates turns back as they enter the lift and sees that the Doctor has scrawled "Get rid of him" on a soapy window. Just as the lift closes, he remembers his attache case and leaps between the closing doors. He just manages to keep from laughing at the Doctor (avoiding a thrashing in the process, most likely). They hurry to his office.
Jo arrives at the pit, carrying a wicker animal cage. Benton wonder what she's up to and she pretends to be looking for the Doctor. He tells her to leave -- it's not safe there.
Yates and the Doctor are discussing his day at Global Chemicals. Yates is convinced Global Chemicals is responsible for the problems at the pit but he can't get any waste or the formula. However, he has learned of a special room on the top floor with its own special lift. He believes Stevens is taking orders from someone on that floor.
Their conversation is interrupted by the arrival of Stevens. Yates grabs his case and heads out with the director while the Doctor pretends to clean.
Cliff Jones is now beside himself with his lack of progress. He happens to glance at the slide that Jo spilled fungus on and puts it under the microscope. To his delight, he sees that it's killing the green slime. He wants to tell Jo the good news but she has left. He finds her note and frantically races off to the pit.
The Doctor has changed back to his regular clothes and is going to the secret room. He uses his sonic screwdriver to operate the lift.
The Brigadier tells Benton that the RAF will attack the maggots.
The boss's voice greets the Doctor as he steps out of the lift into a gleaming room filled with computer equipment. He quickly realizes: the boss is not a man -- BOSS is a computer!
The Doctor has found a secret lift in Global Chemicals leading to the man responsible for the strange events in Llanfairfach. But he is astonished at what he finds out. The boss is not a man -- he is a massive computer!
At the pit, Cliff arrives to look for Jo. Benton doesn't know where the girl is but Cliff spies her on the rocks. Without a word to Benton, he runs after her.
The Doctor is having a conversation with BOSS. The Doctor insists that BOSS is just a machine, but BOSS replies that he is linked with Stevens, which makes him able to transcend logic with inefficient thought. BOSS is convinced that he is the smartest entity on the planet but the Doctor thinks he's just a megalomaniac.
Jo is trapped by several maggots when Cliff arrives to lead her out. But as they try to make their way to safety, the RAF begin their attack, dropping grenades from a helicopter. Cliff and Jo race for safety as explosions surround them. They finally stumble into a cave where Jo tries to radio for help, not noticing a maggot lurking in the darkness.
At Global Chemicals, the Doctor can hear the explosions. BOSS is confident that the RAF will succeed in destroying the maggots.
The Doctor, annoyed with BOSS, present the computer with a riddle -- If the next thing I say is true, but the last thing I said was a lie, would you believe me? BOSS grows confused as the reels on his computer banks begin to spin frantically. The Doctor makes his escape but is cut off by the arrival of Stevens and two guards.
At the pit, the bombing continues. Cliff spots the lurking maggot and throws Jo clear. But he is knocked out by the last bombs from the helicopter, which flies away. The Brigadier surveys the scene with his binoculars -- the maggots are completely unaffected.
Stevens has placed the Doctor in the brain-washing chair, with a headset on the Time Lord. But the brainwashing is absolutely ineffective. The Doctor adds numbers in his head to keep from growing bored with the tedious task of fending off BOSS's clumsy attempts.
Jo is in a tight spot. Cliff won't wake up, her radio is smashed and maggots are wriggling toward the cave entrance.
BOSS finally gives up on brainwashing the Doctor. Stevens tries to explain that what's best for Global Chemicals is best for the world. He will give people freedom from pain and fear. But the Doctor replies that he is giving them freedom from freedom. BOSS tells the guards to dispose of the Doctor but the Time Lord counters that he is more useful as a hostage. BOSS reluctantly agrees.
The Doctor is instead thrown into a prison cell at Global Chemicals. Someone enters the Doctor's cell and the Time Lord attack him. But it turns out to be Yates. He saw the Doctor arrested from the monitors in the director's office. They try to sneak out but are spotted by the cameras. They run for safety as the alarm rings out. A garage door slams shut, trapping Yates. But the Doctor reaches his milk truck and roars off, leaving a trail of broken milk bottles behind him as the guards fire uselessly.
Jo has now repaired the radio and is calling for help. The Doctor arrives at the pit, now in Bessie. He is not surprised that the bombing failed. Suddenly, the radio crackles to life with Jo's call for help. The Doctor decides to rescue her. He drives through the maggots with Sergeant Benton on the radio getting directions from Jo. The Doctor uses his sonic screwdriver to drive the maggots from the entrance while Benton races in to rescue Jo and Cliff.
At Wholeweal, Nancy tends to the injured Cliff. They can't understand what's wrong with him. He wakes up to Jo's voice just long enough to mutter something about serendipity. He then passes out but not before Jo notices a spot of green on his neck.
The Doctor is now struggling with two problems -- healing cliff and stopping the maggots before they pupate. He puzzles over Cliff's words, convinced that they hold the solution to both problems.
Suddenly, Yates appears in the lab. He tells the Doctor that he was let go by Global Chemicals, but then pulls a gun on the Doctor. The Brigadier arrives and the situation almost gets out of control. But the Doctor pulls out the Metabilis crystal. It glows a deep blue, hypnotizing both Yates and the Brigadier.
In the meantime, Stevens has conditioned a new slave named Mr. James.
Yates wakes from his trance. The Doctor tells him that he should go back to Global Chemicals to get more information.
Stevens and BOSS are going over slave numbers from cities around the world when Yates returns He tells Stevens that the Doctor is dead.
Cliff is getting worse despite Jo's attentive nursing. The Doctor is injecting him with antibiotics to gain time.
Stevens wonders if Jo should be killed. Yates objects that it is inefficient, but this arouses the suspicions of Stevens. He calls in James and tells him to wait with Yates.
After Stevens leaves, Mike pulls out the blue crystal and breaks James' conditioning. The disoriented man blurts out that BOSS plans to take over at 4 this afternoon. But a high-pitched wail kills James and Stevens reappears with two guards. He leers at Mike, "You can't depend on anyone -- can you, Mr. Yates."
Captain Yates has discovered the plans of the Global Chemicals computer BOSS to try to take over the world. But before he can escape, a piercing high-pitched wail kills James. And then Stevens appears at the door with two guards. "You can't depend on anyone -- can you, Mr. Yates." Mike has been discovered.
The Brigadier arrives at the Nuthatch with a rock covered in green slime. It's source material for the the Doctor, who is desperate to reproduce Cliff Jones' results in time to stop the maggots and save the Professor. He is puzzled by Cliff's delirious ravings about serendipity.
Nancy, meanwhile, makes a roast out of the brown fungus and puts in on a table to cool.
Benton arrives, carrying something wrapped in cloth -- it is the ruptured husk of a maggot. They are beginning to hatch -- but into what? Before they can discuss it further, they are interrupted by a scream from Nancy. They rush into the kitchen to find a green maggot next to the fungus. But it doesn't move. It is dead. Benton and Nancy suggest that it died from eating the fungus -- which the Doctor notices is covered in green slime.
Stevens and BOSS are hard at work on their plans. BOSS idly wonders how Yates broke his processing. Stevens wants to eliminate him but BOSS decides to give him the total processing which will make him the first of the slave elite.
The UNIT soldiers, meanwhile, are piling sacks of brown fungus into Bessie. The Doctor and Benton drive to the mining pit where Benton starts throwing it out at the maggots, who greedily devour it. They immediately begin to slow down and die. Benton is elated but the Doctor worries about the empty chrysalis. As the drive, they are watched by a massive green and yellow fly.
Cliff continues to get worse, the green rash spreading even as Jo desperately nurses him.
Stevens talks to Yates, who has been chained up and abused. He tells the guards to take him for processing. The drag Mike off, but he is not as weak as he seems. As the lift opens, he pushes them into Stevens and runs off.
Benton and the Doctor are still feeding the maggots. Benton calls to them like hungry cats, which annoys the Doctor. But danger lurks as the massive fly crests a hill and charges after them. They duck as it circles, spraying green slime on Bessie's windscreen. The Doctor throw his heavy coat into the air and the fly smashes into it with a sickening crunch. It falls to the ground, stone dead.
As Yates works on his escape, the Doctor tries to get Jo to figure out how Cliff cured the disease. Jo tells him that she had an accident, spilling fungus all over Cliff's slides. The Doctor drags her to the lab and she shows him which jar she spilled. The Doctor realizes it must be the cure -- it's the same fungus they used to kill the maggots.
The Brigadier is supervising the cleanup of the dead maggots when Yates arrives. The Brig sends Captain Yates to the Nuthatch where Mike tells the Doctor about BOSS's plans. Nancy agrees to finish the cure while the Doctor takes care of Global Chemicals.
BOSS berates Stevens for letting Yates escape. But he is not worried and is ready to go on. The slave units are ready to be activated by seven linked computers. They begin to countdown to activation.
The Brigadier has arrived at Global Chemicals but the guards won't let him in and he's reluctant to use force. The Doctor and Yates arrive in Bessie. The Doctor decides to go in alone, telling the Brigadier that if he's not out by 3:57 to attack the factory and destroy the computer -- the Doctor will be dead if he's not out by then.
BOSS is almost mad -- singing and rhapsodizing happily as his plans come to fruition. He activates the processing of the slave elite. This causes the gate guard to freeze. The Doctor takes advantage and rushes past the motionless guard.
Stevens continues to work, growing frustrated with BOSS's singing and joking. He put on the processing headset.
Jo and Nancy swab a brown liquid on Cliff's neck. It calms him at once. His eyes flutter open and he says hello. He is especially comforted by Jo's presence, kissing her hand in appreciation.
Only six minutes remain before the Brigadier attacks. The Doctor reaches the computer room. But Stevens seems to no longer exist, his mind having been taken over by BOSS. The insane computer mocks the Doctor even as the latter tries to wake up Stevens. He tells them their plan has produced nothing but evil -- maggots, pollution and brainless slaves. He ten pulls out the blue crystal and breaks Stevens' conditioning. Stevens lumps in the chair as the Doctor rips off the headset.
Stevens tells the Doctor to leave and begins cross-feeding the generator circuits to blow up the factory. BOSS is now completely mental, ranting and raving and pleading even as Stevens frantically works the controls. He finally shuts down BOSS and sits down -- tears leaking from his eyes as his only friend perishes around him.
The Doctor emerges from the factory. Everyone dives for cover as Global Chemicals goes up in a tremendous explosion. It's all over.
Cliff is gobbling down the fungus soup, his health completely restored. The Doctor wants to return to UNIT but Jo reluctantly tells him she's decided to stay and go with Cliff to the Amazon. Cliff is enthusiastic and casually mentions that they'll get married on the way. Jo is shocked. The Doctor makes an excuse to leave as Jo happily agrees to marry Cliff. The Brigadier returns and Jo tells him the good news, much to the delight of the UNIT people.
Jo talks the Doctor one last time and expresses her hope that she will see him again. He tells her to save him a piece of wedding cake. He then gives her the blue crystal as a wedding present and they hug tearfully. Cliff brings in some champaign for a toast. As they gather the guests, the Doctor quietly drains his glass and leaves. Jo is the only one who notices -- her expression sad but understanding.
The Doctor walks out to Bessie, takes one last look back and then slowly drives away. Cliff and Jo kiss as the the Time Lord drives off into the Welsh night, alone once more.
|Source: Michael H. Siegel
In between this story and The Time Warrior
, the Third Doctor took a brief spin in the TARDIS himself, during which time UNIT met up with the Fifth Doctor, Tegan and Turlough in Deep Blue
The Seventh Doctor will meet a parallel version of Jo in Blood Heat
, and the Eighth Doctor will meet her and the Third Doctor in The Eight Doctors
, though she doesn't know who he is then. She will later aids the Eighth Doctor and Sam to try and restore all of human history in Genocide
Curiously enough, BOSS is remarkably like the First Doctor's old adversary, WOTAN (Will Operating Though ANalogue) from The War Machines