A downcast young man pace nervously through a quiet corridor. A tone rings out. A woman opens a portal and addresses Citizen Cordo. She congratulates him that his father had died and relief floods him. She tells him Gatherer Hade is waiting to collect the death taxes -- he is to report to the Gatherer's office at once.

Cordo is brought into an opulent office and greeted by a fat pompous overdressed official -- the Gatherer. Cordo is impressed that the Gatherer's desk is made of mahogany -- he's never seen wood or a tree. The gatherer dismisses trees as a primitive way of recycling air -- something they no longer need thanks to the Company. Cordo responds instinctively with, "Praise the Company!"

Cordo has selected the Golden Death for his father -- he long promised him a spectacular funeral. He's told the bill will be 117 talmars, which shocks the nervous little man. He was told it would be 80 but the taxes have been raised. He didn't know because he's been so busy working a double shift to raise the money for his father's funeral. The complex funeral bill is 31 talmars more than he has saved.

The Gatherer condescendingly tells him that taxes are the primary consideration of every citizen. He relents and says he will let Cordo's supervisor assign extra work. Cordo protests that he only has three hours a night to sleep but the Gatherer responds he will have to go without sleep. He should be grateful that he is warm and fed. Cordo disheartedly praises the Company before leaving.

The Doctor is playing chess with the metal dog K-9 in the TARDIS, watched attentively by Leela. He boasts that chess shows the limitations of the machine mind. K-9 promptly announces that the Doctor is in check, with mate in six moves.

The central column stops moving as they play - the TARDIS has materialized. The Doctor checks the instruments and tells Leela they have landed on Pluto. K-9 starts talking about the planet and the Doctor tells Leela to make him shut up about it.

The TARDIS detects a breathable atmosphere and the scanner shows buildings. But the planet should be a lifeless ball of ice and rock. The Doctor decides to take a walk, leaving K-9 to guard the TARDIS.

They have landed atop a bulding. Leela notices the air is like that of Earth -- except for a strange smell. She brings the Doctor to the edge and they gaze down a frightful plunge off the edge. They are atop a massive skyscraper in an enormous city.

As the Doctor gazes at the city, Cordo emerges onto the roof and walks to the edge of the building. He steps over a railing and builds his courage to jump. But Leela spots him and tries to stop his suicide. Cordo tells them he is ready to jump the thousand meters to his death. It's the taxes - he just can't pay them. The Doctor assures him he just needs a good accountant. He offers Cordo a jelly baby and Leela uses the distraction to knock him back over the railing. The Doctor quickly introduces himself and asks for an explanation.

The Gatherer is poring over the accounts when his pretty assistant Marn informs him of an airspace violation and an illegal landing on top of the building. The Gatherer is overjoyed -- both crimes bring a fine of 500 talmars!

Cordo explains the complex tax system he lives under. It is literally impossible for him to pay off the debt since overtime work is taxed, sleep-replacing Q capsules are taxed and the Company charges outrageous interest on debt. Leela suggests the people rise up and slaughter their oppressors.

Sirens rings out and Cordo runs -- the Gatherer is coming. Leela and the Doctor follow. He explains that if he is found there he will be fined and sent to the punishment cells.

The Gatherer and Marn inspect the TARDIS. The Gatherer pretends that he recognizes it.

Cordo calls out for the Doctor and Leela to follow him down into the city before they are caught -- death is nothing compared to the Correction Center. They board a lift and head downward into the depths.

The Gatherer tells Marn they are on the brink of something big. Perhaps this is like the Kandor conspiracy, when a man defrauded the Company of millions. He went on to survive three years in the punishment cells.

The Doctor and Leela wonder why they ran in such a panic. Perhaps everyone runs from the taxman, Leela speculates. Cordo nods in agreement.

Marn wants to look up the records of the roof landing but the Gatherer speculates this isn't a legitimate landing -- it is a smuggling operation. Marn can't believe that someone could be so defiant. He explains that deviance was common before the Company supressed it. But there is always one rotten acorn in every barrel. They must find the conspiracy and crush it.

Cordo has decided to leave the city and join the Others -- outlaws who live in the undercity. Perhaps they will help him. His father told him how to get to the undercity. The Doctor and Leela are eager to investigate which astonishes the meek D-grade worker. It's dark in the undercity -- a prospect which fill Cordo with terror. The Doctor realizes there is no night on the planet and Cordo confirms there are six suns around Pluto - one for each Megropolis city.

They plunge into the dark tunnels beneath the city. Cordo leads them but grows steadily more anxious out of fear of the dark. Just as he decides to turn back, they are surrounded by a group of dirty men. Leela draws her knife but the Doctor has her sheath it.

K-9 emerges from the TARDIS to look for the Doctor. Marn notices the tracker has switched on. It shows K-9 leaving. The Gatherer pretends to recognize the metal dog.

Goudry brings the three captives to the Others' lair. Mandrel, their grubby leader, and Veet, a menacing young woman, are skeptical when the Doctor claims to be from another planet. The Doctor is sarcastic and they thrown him down, demanding courtesy.

K-9 finds the elevator and follows his Master into the depths.

Mandrel thinks the Doctor looks like an "ajack". Leela wants to kill the dirty outsider but the Doctor restrains her. Mandrel continues to ask questions, mocking Cordo as a D-graade worker. Leela tells him Cordo wishes to join their tribe but the young man is too frightened of the dark to speak up. Goudry wants to make the nervous worker into candles and Cordo nervously blurts out his identity. He praised the Company and Mandrel tells him to stuff the Company. Cordo begins reciting his tale of woe and Mandrel mocks him - the taxes are always more than they tell you. Cordo will have to earn his keep with them - not by working but by stealing.

Veet enviously inspects Leela's skins and the girl pulls a knife on her. Mandrel is impressed and thinks the the time travellers could be of some us to him. The Doctor replies they are just visiting but changes his tone when the group closes in around him.

The tracker follows K-9 as he finally comes to the service subway. He can not follow the ladder to the lower levels.

Veet enscribes a complicated plastic block - a credit chit for 1000 talmars. They tell thh Doctor to cash it because he looks like an Ajack - a miner - and they don't. Cordo will take him to a cash dispenser and he will bring the money back. Mandrel marks a candle and explains if the Doctor does not return by the time it burns down, he will kill Leela.

The Doctor climbs back up and notices the air is unscented in the depths. He sees K-9 and remonstrates the dog for leaving the TARDIS.

Marn spots the Doctor on the tracker and also thinks him an Ajack. Hade recognized Cordo from earlier. They wonder what an Ajack would be doing in the undercity. He wants the tracker to follow the Doctor but Marn can't reprogram it. It's focused on K-9. She suggests making direct contact with the Doctor but the Gatherer demurs. THe Doctor might be smuggling weapons. The air conditioning doesn't affect the miners and he has long suspected thaqt any rebellion would start with them. He will warn the Collector - the Inner Retinue are needed to deal with this.

As Cordo watches, guard strap the Doctor to a gurney and wheel him away.

In the Others' lair, the candle runs down. Veet hopes that Mandrel won't damage Leela's skin when he kills her. The warrior assures them that she will see "this rathole ankle-deep in blood" before she goes. Goudry says he won't be the first to attack her.

In the center of the city, a small grotesque bald man - the Collector - huddles over a computer. Gatherer Hade grovels to the Collector but the latter is dismissive, telling him to get to the point. The Gatherer informs him that the Ajacks are rebelling. The Collector is intrigued by this news.

The Doctor wakes in a straight-jacket. Another prisoner - a young man named Bisham - lies on an adjacent bench. He tells the Doctor they are in a punishment area, being sensitized for torture. The Doctor realizes he has been unconscious for over an hour - this must mean Leela has been killed.

Mandrel tells the Others to seize Leela. She throws the first attacker down and pulls her knife. The rest refuse to attack, despite Mandrel's urging. He decides to do it himself but Veet and Goundry plead for more time.

Their fighting is interrupted by the return of Cordo, who tells them what happened. The Others tells Leela the Doctor will get "maximum correction" in the punishment center. He won't survive long.

The Doctor manages to get off of the sensitization couch. Bisham relates that he's being punished for curiosity. He manufactured PCM and took some of the pills meant for executives. When he did, he felt very different - as though he were alive for the first time. He was arrested shortly after. He explains that PCM is a chemical put into the air to eliminate infection. But the Doctor realizes that it also induces anxiety in the workers. He begins to tinker with the torture computers.

The Collector wants to wipe out the Others but the Gatherer says he doesn't have enough men for such an operation. The Collector refuses to expend any additional resources but Hade points out they will gain financially from the move. This piques the Collector's interest - the Company needs to boost output this year. He agrees to loan half a division of his Inner Retinue and instructs the Gatherer to increase the PCM dosage.

Leels tries to persuade the Others to Rescue the Doctor. But they refuse - the Correction Center is under the Collector's Palace and is guarded by his armed Inner Retinue. Leela taunts Mandrel that he has nothing - not even his pride or manhood. She asks if anyone will join her and only Cordo consents. She tells the timid frightened D-grade that he is the bravest man there.

Bisham tells the Doctor that PCM is fed into the Megropolis through the air conditioners. His explanations are cut off by the arrival of a guard who begins work on punishing the prisoners. They Doctor tries to speak to the thug but is ignored as helmets are fitted to the prisoners. The guard goes to the machine the Doctor sabotaged, ignoring the Time Lord's warning. An electric shock knocks the guard out.

Marn informs the Gatherer that the Doctor has been detained and taken for correction. Hade worries that it is too soon -- it will scare off the conspirators. He needs to let the Doctor go to lull his suspicions.

Leela emerges from the undercity and joins forces with K-9.

Technicians work on the machines as the Doctor and Bisham await their punishment. Marn arrives and orders the Doctor released, telling him the Gatherer wishes to meet him. They won't let Bisham go but the Doctor leaves the prisoner a bag of sweets.

Leela, Cordo and K-9 close in on the Correction Center. Leels finds that she is afraid and K-9 explains that there is a chemical in the air affecting her. Reassured, she advances on the Center.

The Doctor is brought to Hade, who greets him warmly as "Citizen Doctor". He is gracious, allowing the Doctor to sit in his chair, giving him a bag of a thousand talmars and apologizing for the mix-up. He tells him that to err is computer, and the Doctor replies that to forgive is fine.

K-9 stuns a guard outside the Correction Center and Leela leads the way inside.

Marn gives the Doctor a raspberry leaf, explaining that it is a luxury on Pluto. The Gatherer explains that most people aren't even aware that they came from Earth. Hade himself isn't quite sure why they left the planet. The Doctor departs, giving the Gatherer a jelly baby.

Marn reports that the tracker is now keyed to the Doctor. They believe him totally fooled by their act.

K-9 searches the Correction Center, following the Doctor's trail. Bisham is patiently awaiting his torture when Leela breaks in and shoots the technician. She frees Bisham and asks about the Doctor. He tells her of the Doctor's release and doesn't know where he's gone. Cordo's nerve is finally breaking and they decide to leave the Center.

The Doctor returns to the undercity, where the tracker can't follow. Marn worries he might be organizing resistance there and the Gatherer decides to have a section of the Inner Retinue go through the heating ducts and wipe them out. But he will attack only after they have identified all the conspirators.

The guard outside the Correction Center awakes and sounds the alarm.

The Others are eating revolting food when the Doctor returns. He tells them what happened and throws the thousand talmars down. Mandrell is deeply suspicious. The Doctor ask about Leela and Goudry tells him where the girl has gone. The Doctor confronts Mandrell who fires back that the Gatherer never gives anyone money -- the Doctor must be a spy.

Leela makes K-9 hide as the guard approaches. The robot then shoots both the guards when they are close enough. She takes the cart and has Bisham drive through the barrier. But as she turns back, a shot hits her head, knocking her from the cart. Bisham has no choice but to continue driving as the guards close in on Leela's prone body.

Mandrel asks the Doctor why the Gatherer gave him the money. The Doctor replies sarcastically and is struck. Mandrell accuses him of making a deal with the Gatherer. He has Goudry hold a hot iron over the Doctor's face and gives him one last chance. The Doctor finally tells him he has no idea why the Gatherer gave him the money. Mandrell doesn't believe him and counts down to torturing him. The Doctor doesn't believe he'll do it and help him count down.

They are interrupted by the return of Bisham and Cordo, the latter holding a gun on the leader of the Others. The Doctor asks where Leela is.

Leela is taken to the Correction Center. The interrogators inform the Collector that she's not numbered -- all work units are numbered at birth and she shows no signs of having it removed. The Collector wants her treated and brought to him.

The Doctor talks to the Others, trying to persuade them to rebel. The first step is to stop the PCM from entering the air system. There are eight circulators. But Mandrel - who admits to having been a B-grade controller - tells them they are all controlled from one point. The Doctor is right -- it could work. They would need to take over Main Control but it is only guarded by two men. Goudry is opposed but the Doctor asks them what they have to lose? Only their claims.

The Doctor thinks they can easily beat the Company if they stand up for themselves. The first step is to disable the camera system, which is fixated on him. He sends Cordo to retrieve two of the cameras. Bisham tells him that he thinks Leela is alive, but a prisoner of the Collector.

Leela is dragged into the Collector's office, bound and struggling. He asks her name and place of birth and becomes convinced she is from a distant colony. She tells him she arrived with the Doctor -- a Time lord -- and broke into the Correction Center to rescue him. The Collector, having enough information, has her taken away. He then asks the computer about Time Lords and it tells him they rule Gallifrey and have a low commercial potential.

Encouraged by Cordo, the Others have agreed to help a rebellion against the Company. The Doctor asks where the Company came from and they don't know. All they know is that it makes a profit. He tells them to go through the city and encourage resistance.

The Gatherer visit the Collector, who wants to know why he released the Doctor. The Gatherer happily explains his conspiracy theory but the Collector dismisses it -- the Doctor is an alien who landed on Pluto by mistake. He tells the deflated Gatherer that the Doctor has a long history of violence and economic subversion.

He tells the Gatherer to offer a 5000 talmar reward for the Doctor -- paid of of Hade's own account. He also instructs him to send out a notice of a public execution of the girl, with a 5 talmar charge for attendance and a two hour unpaid public holiday. The computer indicates the Doctor will try to rescue her. With any luck, they will be able to roll both of them into the steamer.

Cordo replaces the cameras and the Doctor walks up and down between them while K-9 monitors. He then sets off for the Correction Center.

Leela is tied to a wall. A guard gloats that she is to be executed by steaming. When she admits she doesn't know what that is, he laugh uproariously.

Marn tells the Gatherer they've found the Doctor. The camera shows him walking back and forth between the two cameras. Hade grabs a gun and goes to arrest the Doctor himself to make sure no one collects the reward.

A pair of technicians is working in Main Control when a mugshot of the Doctor is posted along with the reward. As they watch, the Doctor appears and scoffs that the reward is an insult -- someone once offered an entire star system for his head. Bisham, Cordo and Mandrell arrive next, holding weapons. They tell the technicians to join or die. The techs agree and Mandrell shuts down the PCM system.

Marn and the Gatherer pop into the hallway but is is empty. Marn checks the scanners, which insist that the Doctor is walking back and forth.

A mugshot of Leela is broadcast along with the announcement of her execution. The Doctor asks Mandrell to cut the water supply to the steam pumps but Mandrell tells him the heat exchanger would blow and take half the city with it. The Doctor says he just needs a few minutes to crawl through the main pipe and free her. Mandrell counters that the pressure inside the pipe would kill him and can only be released from the inside. K-9 volunteers as he is sturdy and could blast the valve open.

Leela is placed in the steam chamber. The Collector and Gatherer eagerly await her screams of agony.

The pressure drops as K-9 blasts the valve. The vent is opened and Mandrell reverse the pumps. The Doctor has two minutes to get to Leela before the exchanger explodes.

Vibrations begin to sound through the city as the pressure builds in the heat exchanger. The Collector is annoyed with the noise -- he won't be able to hear Leela's cries.

The Doctor finally breaks in and releases Leela. Mandrell caves in and calls to the Doctor over the microphone, telling him the chamber will blow soon. The Doctor destroys the microphone but it is too late -- the audience has heard. The Collector orders his guards to investigate.

Mandrell finally releases the pressure, unsure of whether the Doctor made it out or not. Sounds from the vent let them now he is alive and they let him and Leela out. The Doctor is angry that he used the radio link.

Bisham tells the Doctor the PCM is already clearing from the air. The Doctor asks where the public video is run from and is told it is in the Collector's office. The Doctor proposes that if they announced a successful rebellion, the people would believe it. The Collector's Palace is usually guarded by his Inner Retinue but most of them are with him in the execution chamber.

A couple of guards wander in and are caught. The Doctor expect a full attack and tells them to hold out as long as they can. He leaves with Leela, telling K-9 to help the rebels.

The Collector is upset that he received no satisfaction from the execution -- and they gave the workers a holiday for it. They will have to make it up with unpaid overtime.

A guard reports there have been minor disturbances -- workers refusing to leave their dormitories. A division of the Inner Retinue will be needed to settle the matter and more taxes raised to pay for it. The Collector is convinced that the Doctor is behind this. He tells Hade to investigate Main Control.

The rebels in Main Control are giddy now that they are freed of the PCM. Mandrel tries to keep them focused on the rebellion.

A group of guards tells some lounging workers to get back to their jobs. But Goudry and Veet encourage the workers to strike. They tell the guards they can join or leave. The guards try to arrest them and are grabbed by the mob.

Leela knocks out the guard in the Collector's office. She wants to kill him but the Doctor stops her. She reminds him that the last one she spared raised the alarm but he hypnotizes the guard to sleep. Unfortunately, he puts Leela to sleep too. He covers the guards ears and tells her to wake up. Leela shows him the Collector's desk.

Hade reports that the situation is getting bad. There is laxity an weakness everywhere, which the Collector believes is the result of too much kindness. The guards are outnumbered, reports Hade, and he will need two divisions of the Inner Retinue to quell the rebellion. Marn then reports that workers are on the roof gazing at the Sun. Hade is outraged -- the sun too good for them!

The Collector decides to return to his Palace and implement his contingency plan. He has his Inner Retinue guard his return.

As the Doctor tinkers with the Collector's computer, Leela finds a safe. The Doctor uses the sonic screwdriver to break into the vault but hesitates going through the door. Leela rushes in and is knocked out by a bolt of electricity. The Doctor deactivates it and makes sure she's all right.

The PCM levels continue to drop. An announcement on the PA claims that the Megropolis is under the control of the revolution. Guards are ordered to lay down their arms and join the citizens. Marn is corned by a group of citizens and elects to join.

Cordo comes into the Main Control and fires his gun into the roof in celebration. Bisham reminds him that they haven't really won -- it's just the Doctor trying to encourage people. They decide to take the fight into the streets, leaving K-9 to defend Main Control.

The Gatherer reaches the roof and demands that the workers leave. Veet spurs them on and they grab Hade and toss him over the railing to his death. They boast they'll do the same to the Collector when they find him.

The Collector returns as the Doctor investigates the safe. The little man is hardly surprised to see the Doctor there. The Doctor sits next to him and explains that he's not going to kill him, just shut him down. The Collector craftily offers him the Company prospectus, hoping to pique the Time Lord's interest.

The Collector hits the alarm but the the button just pops out humorously -- the Doctor disabled it so they wouldn't be disturbed. The Collector asks for terms and the Doctor asks about the Company. The Collector happily explains that Company is based out of Usarious. The Doctor recognizes the planet and remembers that it is inhabited by poisonous fungi.

The Collector tells him that the Company was looking for property and Earth was running out of resources. So they made a deal. They moved all the people to Mars, terraformed the planet and then taxed the life out of them. Pluto was the next step. But once Pluto runs out of resources, they will simply let humanity die out. They aren't that profitable anyway. The Doctor, outraged, calls him a blood-sucking leech. The Collector retorts that economics are far more profitable than war.

They hear shots approaching but the Collector is certain the revolution will be quelled. The Doctor tells him to wake up, accidently reviving the guard. The Collector tells him that if they can't quell the rebellion, all the people will die. As the guard holds his gun on the Doctor, the Collector explains that his contingency plan will release a deadly poison in the Megropolis killing everyone within 10 seconds -- except for the Collector, of course, who doesn't breath.

The guard, hearing this, hesitates and Leela, having revived, knocks him out with her knife. The Collector reaches for the death switch but Leela slams the door on his hand.

The Collector begins to sputter and stammer. He turns green as the computer reports the planet is no longer profitable. Cordo arrives with the mob and tells the Collector, in the name of the works units -- people, reminds Leela -- to surrender.

But the Collector, facing a negative profit spiral, shrinks down, turns green and reverts to a small fungus that trickles through a hole in the chair. The Doctor explains that this is the Collector's natural state and the image was needed because no one would take orders from a lump of seaweed. He corks the hole, trapping the Collector in his chair.

The Doctor, back on the roof, bids farewell to the rebels. He promises to visit once they've resettled Earth -- which should be replenished by now.

Back in the TARDIS, he promises to continue his chess game with K-9, who reminds him it is mate in six. The Doctor explains that he put a negative tax into the Collector's computer that caused him to project negative profits. This upset the little creature so much that he lost control.