Inferno ( TV story ) Inferno was the fourth and final story of season 7 of " Doctor Who " . It was the last story to feature Caroline John as Liz Shaw , although her departure is not depicted . It was also the first " Doctor Who " story to explore the concept of parallel universe s . " Inferno " was the first story in which producer Barry Letts had any say on development and commissioning . Director Douglas Camfield suffered a minor heart attack after completing the location filming and the studio scenes for episodes one and two . This left Letts to direct the studio scenes for the remaining five episodes . Several possible stories were considered for the season finale . " The Mists of Madness " by Brian Wright and " The Shadow People " by Charlotte and Dennis Plimmer were two . However , Wright was unavailable , and the Plimmers abandoned the project after a pay dispute . This left the way open for " The Mo - Hole Project " , as it was then titled , by Don Houghton . The serial went through several name changes before becoming " Inferno " . Houghton had based the drilling part of the story on real events . He had contacted the American Embassy to enquire about , a real world attempt to drill through the Earth ' s crust . Information on the project and why it was abandoned were not disclosed as such information was top secret . It was this secrecy that Houghton developed for his story . Letts was worried when the first script draft arrived as he did not think there was enough in it to fill a seven - parter . Additions such as the Primord s and scenes featuring Venusian aikido were made to suitably lengthen the script . Synopsis . UNIT is providing security cover at an experimental drilling project designed to penetrate the Earth ' s crust and release a previously untapped source of energy . Soon , however , the drill head starts to leak an oily green liquid that transforms those who touch it into vicious primeval creatures with a craving for heat . The Doctor is accidentally transported by the partially repaired TARDIS control console into a parallel universe where the drilling project is at a more advanced stage . Thwarted by his friends ' ruthless alter egos , he works to save both universes . Plot . Episode 1 . The Doctor drives Bessie into an area marked restricted . A maintenance worker by the name of Harry Slocum enters a drilling unit nicknamed Inferno . He introduces himself to Sir Keith and is told there is an issue with pipe number two . He is urged to fix it quickly , as Professor Stahlman does not want any delays . The Professor is at loggerheads with Sir Keith and tells him he should never have stopped the pipe for maintenance . He tells Sir Keith never to make a decision with regards to the drilling again . As Slocum is fixing the pipe , he sees a green goo emanating from the base . He touches it , and it burns . He is horrified to see his hand turn green . Sir Keith discusses the Professor with his personal assistant Petra . He confides that he has sent for an expert in oil rig mining , Greg Sutton , as he is nervous that there is no one with real drilling expertise on the mission . As Slocum leaves , he seems entranced . He heads outside the complex and stumbles against a piece of scaffolding . A man rushes out to help him . With a growl Slocum turns on him and kills him with his wrench . In a room inside the complex , Benton is hanging a picture in what is to be the UNIT HQ . The Brigadier enters and asks if there has been any sightings of Slocum . Benton says there hasn ' t been . The Doctor enters , and the Brigadier tells him of the murder . He shows him the wrench . It is still warm and , when it was found , it was red hot . The Brigadier comments that trouble seems to follow the Doctor around , and he questions why he asked to be on this mission . The Doctor says that an opportunity to be at the first penetration of the Earth ' s crust was not to be turned down . He heads off to do some experiments of his own . Sutton has arrived and is bewildered at having been pulled over with such urgency . Sir Keith shows him around the complex . He says that the drill head is twenty miles deep . This has been achieved by having no pipes , the pipes visible containing coolant delivered to the drill bit . Instead , there is a robot drill that is fed by a cable from a nuclear reactor . Sutton asks what this is hoping to achieve . The project is aiming to pipe Stahlman ' s gas ( named after the Professor ) , a powerful energy source trapped inside the Earth ' s crust since the dawn of time . Sir Keith begins to introduce Sutton to the staff . He tries to flirt with Petra and is snubbed . On introduction to the Professor , he is cold . The Professor thinks that Sir Keith is trying to introduce as many experts into the project as he can to try to close it down . He counts the Doctor as one of these . Sir Keith introduces Sutton to the Doctor and asks his opinion on the project . He says that they should be heeding the warnings of the computers . As he leaves , he overhears the Professor complaining about the experts to Petra . He causally , but loudly , points out a flaw in the mechanics to a near by scientist , causing the Professor ' s blood to boil . The Doctor pulls up to a small building being guarded by a UNIT soldier . He asks if there is any news about Slocum ; he is told that there isn ' t . The Doctor uses a device to open the door to the building remotely and drives Bessie in . Liz is inside working on the TARDIS console . The Doctor hands over the figures from the computer and tells her of the murder . She already knows as the sentry told her . They discuss the real reason they are here . The Doctor wants to use the nuclear power to try to jump start his TARDIS console . He wants a test run straight away . Liz starts flicking switches and positions herself by the main switch . Slocum is skulking around the complex . He is now covered in hair and has claws . He enters a building . A member of UNIT is on the phone . Slocum approaches him from behind . The Doctor says he is ready . Liz pulls the lever down . The machine registers 7 mega volts . Slocum has killed the UNIT soldier . He pulls a switch down to maximum . The console begins to shake . The Doctor says that there is too much power . Liz cannot do anything as the circuits are locked . The console and the Doctor dematerialise . The Doctor is in some kind of limbo and is in some pain as he and the console fly through the darkness . He flies off into the black . Liz uses a plank of wood to force the levers down . The Doctor and the console reappear . The Doctor is groggy but fine . He is keen for another trial run . Liz tries to dissuade him , but he says he needs to know where he was . An alarm goes off . It is the drill head . The Doctor and Liz hurry off to Bessie . The complex is in lock down as the drilling room fills with smoke . The Professor argues with Sir Keith as to why he ordered the lockdown . Sir Keith implores him to shut off the power , but he refuses . Sutton says that if the power is stopped now , it will never be able to be restarted again . Petra is ordered to check the coolant . Sutton tries to stop her , saying that the pressure is too dangerous , but she doesn ' t care . The Doctor and Liz enter . The Doctor says that there has been a nuclear power surge . The Brigadier enters and says that there has been another murder . The Doctor goes to the Professor to give him his advice , but he tells him to stop wasting his time . The Doctor heads off with the Brigadier . Petra returns , saying that the controls are jammed with the heat . Suffolk tries to stop her from heading off but instead goes with her to help . They find the Professor trying to stop it manually . Sutton helps . The Doctor and the Brigadier go to examine the body . As they do , Slocum jumps up , growling . Episode 2 . The Doctor stops any UNIT forces from attacking . Sutton has sorted the issue with the coolant . The Professor says the readings are too high . He gets offended when Petra suggests they need the Doctor . The Doctor tried to calm Slocum . A UNIT soldier , Private Wyatt , sneaks up on Slocum and prepares to attack . The Professor is trying to contact the Doctor . The phone is ringing but all ignore it . Slocum attacks Wyatt . Wyatt manages to shoot him twice . They wrestle , and then Slocum slumps to the ground . Sir Keith wants to stop the drilling , but the Professor blocks it . Slocum is wounded but alive . The Doctor wants to turn off the switch but can ' t as it is too hot . He borrows the Brigadier ' s gun and uses that . Slocum dies . As he slumps down , the wall he was leaning on is blackened and scorched . The Doctor answers the phone and tells the Professor he has sorted everything . The Professor tells his workers to return to their duties . Sutton is cross at him and says he is just asking for trouble . He tries to confide with Petra and implores her to try to persuade the Professor . The Doctor and the Brigadier examine the body . He was shot twice through the heart but remained alive for several minutes . The Doctor marvels at his abnormal resistance and strength . The body is still hot . The attacked UNIT scientist and Private Wyatt are seemingly fine . The Doctor and the Brigadier climb to the roof to discuss what is going on . The Doctor suggests that there is some kind of retrogression of body cells that causes the victim to turn into animals . The Doctor says that it is a very slow process and wasn ' t complete with Slocum . The Brigadier asks if he has ever heard a noise like the one Slocum made . The Doctor says he has , at Krakatoa in 1883 . The Brigadier asks if there is a link . They are interrupted by a UNIT soldier , who reports that Wyatt has disappeared . The Brigadier and the soldier rush off to find him . The Doctor sees him high above on a walkway and pursues him . When he catches up , Wyatt is animalistic . He approaches the Doctor , wielding his gun like a club . He swings too hard and throws himself off the edge of the walkway . The Doctor shouts for no one to touch him . The UNIT scientist emerges from the building in a trance . The Professor wants to increase the drilling speed . Petra calls him into a room where Sir Keith and Sutton are examining something . They open a box and show the Professor a vial of the green goo . Sir Keith says that it has defied analysis and that it is very tricky to analyse as it is too hot and does not cool down . The Doctor tries to suggest what it is , again mentioning Krakatoa . The Brigadier wants to talk to the Professor and Sir Keith . The Professor is reluctant to comply . The Brigadier insists . Left alone , Liz and the Doctor discuss the substance . The Doctor says he wants to hear it as he thinks it will let off a scream . Liz asks him to come and look at one of the computers . The Professor is callous and is not bothered about the deaths on his site . The Brigadier and Sir Keith plead with him to show more mercy . He says he has no time for these deaths nor any crazy theories of the Doctor ' s . The Doctor enters and asks if the Professor ever intends on paying heed to his computers . The Professor insists that the computers are over sensitive . The Doctor reacts angrily . Petra rushes in and says that the vial holding the green goo is about to break . The Professor strides out and , against the Doctor ' s suggestions , takes the vial in his hands and puts it back into the box . He orders it to be deep frozen . The Professor makes it clear that his discussion with the Brigadier is over and that the computer is faulty . The Doctor shows the Professor the computer and warns him that he should stop the drilling . Again , the Professor says that the readings are inaccurate . The Doctor goes to leave . The Professor tells him that he is taking away the nuclear power that he has been using to experiment with the TARDIS . The Doctor tells him that he is being childish . The Professor tells Petra that they can up the work rate of the drill in 25 minutes . Petra asks if it is safe , but the Professor disregards her . As he is left alone , he discovers that his hand is green . The Doctor asks Liz to go back to their hut and test the tri - gamma circuits on the console . Subtly he flicks a switch on one of the computers and poses his hut back up . The Professor enters and opens the computer and removes a microcircuit . He finds a truncheon in the Brigadier ' s desk and goes to smash it . The Doctor stops him . He goes to do it again , and the Doctor uses Venus ian karate to paralyse him . The Brigadier breaks it up . The Professor leaves , saying that the Doctor is a mad man . The Doctor tells the Brigadier what he saw . When they challenge him , the Professor accuses the Doctor of trying to sabotage the drilling . They check his pockets , and he no longer has the microcircuit . As the Doctor leaves , he points out that the computer has already stopped working . Unseen , the Professor stamps on the microcircuit which he had dropped on the floor . The Doctor returns to his hut . Liz has fixed the tri - gamma circuits . She asks why he asked her to do it , and he says he strongly believes that the console is fine ; it is just the nuclear surge that ruined his test . Liz says she is relieved they can ' t test again . The Doctor sends Liz off to run some tests through the computer . As soon as he is alone , he busies himself with the console . As Liz leaves , she is pursued by the animalistic form of the UNIT scientist . Liz returns to find the computer broken . When she explains to the Brigadier why she is there , he says that the Doctor knew the computer wasn ' t functioning . Liz rushes over and sees that the switch to provide power to the Doctor ' s hut is on . She and the Brigadier run off . The Doctor hangs onto his console as it begins to shake . The Professor notices that the power is down . He runs over to the switch and switches the Doctor ' s power off . Liz and the Brigadier return to see the Doctor and his console dematerialise . Episode 3 . Liz tries to bring back the now disappeared Doctor , but there is no power . He is trapped . Liz and the Brigadier return to the base . The Brigadier orders the Professor to reconnect the power and explains why . He refuses . Sir Keith threatens to tell the Ministry about this and the new mining speeds . The Professor tells him to do so . When the Professor leaves , Sir Keith says he will go to London as soon as possible but can ' t leave the Professor to do as he pleases at this critical point of the drilling . The Professor ' s hand is now bright green . As he puts some gloves on , he is seen by Petra , who tells him to get it checked . He tells her not to worry . Liz berates the Brigadier for not showing concern over the Doctor . The Brigadier says he has many concerns of which the Doctor is one . The Doctor awakes . His surroundings are somewhat altered . On the wall is a poster that reads " Unity is Strength " . His device does not open the door , so he forces it open . The shed door has a sign reading " Technical Store " with an unfamiliar logo on it . He drives Bessie out of the garage and pauses to close the door when he is shot at by soldiers . After protesting , he jumps aboard Bessie and drives off , pursued by the soldiers , who consider him a saboteur . He soon finds himself in a dead end where a soldier jumps aboard Bessie . The Doctor and the soldier fight as the Doctor drives . He manages to throw the soldier out of the car . He parks Bessie between some houses and hides in a bin . The pursuing soldiers run into the house , allowing the Doctor to escape . The Doctor sneaks onto a walkway above the compound and watches the soldiers look for him . He hears a snarl behind him , and one of the animalised humans approaches him . As he attacks , the Doctor uses a fire extinguisher to subdue him . This draws the attention of the soldiers , who continue to pursue him . Another animalised human approaches him . The Doctor counters his attack with a wooden pole . Below , the soldiers are ordered to shoot on sight . They see a figure above them and shoot . The animalised human falls to the ground . A female figure marches though the compound . The Doctor sees that it is Liz , only with a different haircut . The Doctor draws attention to himself and asks why she is wearing those clothes . The woman looks confused , draws a gun and blows her whistle for backup . She orders they take him away . The Doctor is brought into the Brigadier ' s office , where he is met with a figure similar to the Brigadier but with an eyepatch and a large scar by his eye . He asks how the Doctor got in . The Doctor responds quizzically and asks who he is . The man reveals himself to be Brigade Leader Lethbridge - Stewart , while the woman is Section Leader Elizabeth Shaw . When he asks who the Doctor is , the Doctor realises what has happened . He introduces himself as Doctor John Smith and says he is from a parallel space time continuum . The Brigade Leader is unsure if he is mad or bluffing . The Doctor shows he has knowledge of the drill and the people running it . He wants to see Professor Stahlman or Sir Keith . The Brigade Leader takes him to Director Stahlman . On the way , the Doctor notices that the drilling is three hours and twenty minutes away from the core , much in advance of where the Doctor has come from . When the Doctor is brought to the Director , he asks to see Sir Keith . The Director tells him that Sir Keith was killed in a car accident on the way to the ministry in London . The Doctor draws attention to the broken computer that was giving out warning signs before it broke down . The Director accuses the Doctor of having broken it and calls him away . He turns to Doctor Petra Williams , the Assistant Director of the project , and asks her to continue the drilling . Sutton tells her that there is no pressure getting to the drill head . Doctor Williams tells him that she is aware of this . Doctor Williams tells the Director what Sutton told her . He refuses to decelerate . Once he is left alone , he feels a pain in his hand . He takes off the glove , and it is bright green all over and hairy . The Doctor is being made to wait by the Brigade Leader . He asks what is going to happen to him and is told that he will be executed without trial under the Defence of the Republic Act 1943 . When the Doctor asks about the royal family , he is told that they were executed . When the Doctor tries to sit down , he is forced to his feet by the soldiers . When he badmouths them , the Brigade Leader tells him he cannot insult the Republican Security Forces who have been brought here to protect the drilling . The Doctor says they will need protecting if the computer that was giving out danger signals or the death of Harry Slocum is anything to go by . The Brigade Leader says he is showing the amount of knowledge that only a spy could possess . The Doctor insists that he has seen it all in his world . The phone rings , and the Brigade Leader rushes out . Elizabeth tells him that Central Records have returned no match for the Doctor . This confuses the Brigade Leader as Central Records have never failed him before . They both interrogate him . Doctor Williams is informed of a minor leak in the drill head . Sutton questions her and is frustrated when neither she nor the Director seem to be bothered . An alarm goes off . Hearing the alarm , the Brigade Leader and Elizabeth rush out . The Doctor calls over the guard and immobilises him with karate . Smoke and green goo are pouring out of the drill head . The Brigade Leader is ordering all of his men and all of the scientists to remain at their posts . Amongst this chaos , the Doctor sneaks forward . Sutton orders the scientists around , to no avail . Doctor Williams watches the reading increase . The scientists start to abandon their posts ; the Brigade Leader threatens to shoot them . The Doctor has found a toolbox and is scrabbling around looking for a microcircuit . He is discovered by a member of the Republican Security Force , who holds a gun to his head . The Doctor implores with him , saying that he knows how to stop all this . The guard is unmoved and asks him if he is going to come with him quietly . Episode 4 . Elizabeth stops the soldier . The Doctor thanks her , but she says that she only did so because it goes against procedure . The Doctor tries to buy time to fix the computer , and eventually Elizabeth allows it . The computer begins to work and assesses the problems . The Director is angry that the Doctor has been allowed access to the computer . Sutton and Elizabeth stick up for him . Sutton and the Dictator argue about the safety precautions . Doctor Williams starts to listen to the Doctor ' s theories . The Doctor says that the heat and the pressure is proving too much for the velocity of the drill and that the only way to counteract it is to produce a reverse vortex by reversing all the systems . Reluctantly the Director agrees , then sends the Doctor away . Elizabeth compliments the Doctor , and then asks where he came from . He repeats his story about the parallel universe . She asks about the version of herself in the Doctor ' s universe . He says that she is a scientist . Elizabeth says that there is no similarity . The Doctor asks if she every contemplated being a scientist , and she admits she studied physics at university . The Doctor points out that it is there where the two points diverged . Elizabeth is doubtful , but the Doctor encourages her to think for herself . Doctor Williams and Sutton talk about the Doctor and his motivations for saving them . Sutton says he intends on cutting the drill down to minimum speed , regardless of what the Director thinks . Doctor Williams tells Sutton that he needs to start towing the line a little more . Sutton refuses , despite knowing that those that disobey orders " disappear " . Elizabeth is told that the emergency is over , thanks to the Doctor . The Doctor warns Elizabeth about the dangers of the drilling operation . The Director asks Sutton for progress and is told all is well . The Director tells Sutton he intends on increasing the drilling speed . Sutton says that this is madness . The Director threatens to dispose of Sutton if he continues to disobey him . The Brigade Leader and Elizabeth are firing questions at the Doctor . They ask him his name , who sent him , whether he is a saboteur , what organisation he works for , whether he is a traitor , how he gained access to the complex , who helped him and which of their enemies he is working with . The Doctor does not answer . Elizabeth warns him they have other methods of extracting this information and repeats the question . The Doctor says that he came on his own , by accident , and has slipped sideways through time . Elizabeth asks the Brigade Leader for permission to go to stage two interrogation . He blocks this , as he is fearful the Doctor will die before talking . The Doctor hears the acceleration of the drilling and rises to try to stop it . The interrogation continues . The Director enters , wanting to know what progress is being made . The Doctor draws attention to the Director ' s gloves and challenges him to take them off . The Director tries to brush over this , but the Brigade Leader asks him to . He does so , and his hands are bandaged underneath . He says that he scorched them . The Doctor begins babbling about the green goo and infection . The Brigade Leader orders the Doctor to be taken to the Security Centre and asks Elizabeth to supervise him into his cell . When they are alone , the Brigade Leader questions why the Director is so concerned about the Doctor . The pair squabble , and the Director leaves , saying he wants the Doctor " liquidated " by the end of the day . Sutton and Doctor Williams conspire about the Director . Sutton is questioning why he is continuing to up the speed of drilling . Doctor Williams appears convinced by Sutton . The Doctor is escorted to his cell by Platoon Under Leader Benton . He notices he has a sleeping figure in the cell next to him . Platoon Under Leader Benton says he will be sleeping for some time , as he has been shot with a tranquilliser dart . Elizabeth comes to check on him . The Doctor refuses to be interrogated any more , until Platoon Under Leader Benton orders him to his feet at gun point . Again , Elizabeth asks who the Doctor is and how he came to the complex . The Doctor , again , tells the truth . Platoon Under Leader Benton asks for a moment alone with the Doctor to extract the information from him . Elizabeth sends all the guards away . She puts to him that he is a protester from a free speech group who is forming a demonstration and that if he confesses to that he will only get a few years in a labour camp . The Doctor refuses . Elizabeth says she will leave him to the Brigade Leader and leaves . Left alone , the Doctor tries to talk to the sleeping figure . After no response , he goes to sleep . A green hairy hand emerges from beneath the sheets . Back in the Doctor ' s universe , the Brigadier tells Liz that the UNIT soldiers have searched the entire complex for the Doctor , to no avail . They will not extend their search beyond the complex . Liz is concerned that the Doctor could be anywhere in space or time . When the Brigadier says that the Doctor can look after himself , Liz warns that he is not indestructible . Sir Keith asks the Professor if there are any problems or precautions with the drilling . He responds in the negative to both . Sir Keith says he is going to London and , unless he receives some kind of assurances , he will tell the minister of the unsafe practices being carried about by the Professor . The Professor says he has no intention of playing it safe . When the Professor leaves , Sir Keith tells the Brigadier and Liz that he is not sure that the Minister will even listen , as he has been blinded by the Professor ' s promises of free energy . Sir Keith has an ominous feeling about the whole thing . In the parallel universe , the Doctor awakens to snarling from the sleeping figure . He calls for the guard , who enters to investigate . He is attacked and killed by the animalised human under the sheet . The creature approaches the Doctor and bends the bars to enter the Doctor ' s cell . The Doctor flips his mattress onto the creature , knocking him over . The Doctor escapes , locking the door behind him . He runs into the complex and approaches a truck . He is surrounded by people and in an effort to hide gets into the back of the truck as it drives off . The drill is thirty five minutes from the centre of the Earth . Sutton asks Doctor Williams if everything is ready . Sutton has an ominous feeling about the whole thing and thinks they should be paying more attention to the computer . The Doctor has found a full radioactive security suit in the back of the truck . A guard discovers the carnage in the cell . The truck draws up and the Doctor exits , dressed in the security suit . The drill is three minutes from the centre of the Earth . The Director stares intently at the readings . The Doctor renters the compound with other similarly dressed men . The drill is two minutes from the centre of the Earth . The disaster crew is at action stations . The Doctor and the other similarly dressed men enter the main area and line up . The Doctor sneaks away and begins to tamper with a computer . The drill is one minute from the centre of the Earth . The Brigade Leader notices the Doctor and calls to him . The Doctor unveils himself and shouts that the countdown should be stopped . The Director orders the Doctor to be shot . The Brigade Leader draws his gun . Sutton protests . The Doctor warns that they are about to release forces that they ' ve never dreamed of . The drill lets out a high pitched whine . The Doctor warns that it is the planet screaming out in rage . Sutton attacks the Brigade Leader and implores the Doctor to run . Wherever the Doctor turns he is blocked by resistance security forces . The Director now has the Brigade Leader ' s gun and is pointing it at the Doctor . The countdown reaches zero . Episode 5 . The ground beneath them shakes , and they all fall to the ground . Everyone around them screams and abandons their posts in panic . The Brigade Leader attempts to stop them . The Doctor staggers to his feet and tries to stop Sutton from going in . The Director is attempting to as well . The Doctor questions that it seems that the Director is not feeling the heat quite as much . Doctor Williams confirms that nothing can be controlled remotely . Inside the drilling station , there is a huge explosion , and the green goo bubbles out of the drill . Sutton and the Doctor enter in their security suits . Sutton is struck about the head by the Director . Whilst Sutton is unconscious , the Director removes his helmet . The Director and the Doctor have a fist fight . The Director is winning when Sutton staggers to his feet and strikes the Director over the with a metal pole before collapsing in the fumes . The Doctor helps Sutton out . When the Doctor tells everyone what the Director did , they want to go in there and save him . The Doctor comments that he seems to like it in there . Sutton and the Doctor prepare to go back in when the door is closed from the inside . Inside , the Director is purposely contaminating people with the goo . The Doctor asks how thick the door is . Sutton replies that it is enough to stop a nuclear explosion . The Doctor warns that it will not be enough . An explosion rocks the complex . The Brigade Leader returns to say almost everybody has abandoned their post . Doctor Williams says that the computer is broken . The Brigade Leader reports of seismic tremors and earthquake s all over the country . The government have put him in control . Sutton asks if they have any plans to seal the shaft . The Brigade Leader says they do not . Sutton asks the Doctor if it is possible . The Doctor says that no substance in the world is strong enough to withstand the unleashed energy . The pressure will only get worse until , in days or weeks , the Earth will dissolve . An animalised human has appeared behind them . The Brigade Leader goes to attack it , against the wishes of the Doctor . The Brigade Leader tries to shoot it , to no avail . The Doctor uses a fire extinguisher , which immediately kills it . The Doctor explains that the creatures can ' t stand the cold . Sutton wants to leave . Doctor Williams says she will accompany him . The Brigade Leader draws his gun on them . Platoon Under Leader Benton says he has found some resistance security forces . The Brigade Leader tell him to ensure nobody leaves the building . Platoon Under Leader Benton marshals his troops . Doctor Williams is attempting to fix the computer . Sutton says there is no point and that they are all going to die . Doctor Williams the whole complex needs re - wiring . Sutton says there is no chance of that as the government has abandoned them . Sutton softens his tone when he sees how distressed Doctor Williams is . She now realises that it is the end . She and Sutton embrace . Sutton says he plans to leave and asks if she wants to come with him . Elizabeth is losing her mind at the planet ' s imminent demise . The Doctor says they still have a chance to save the other world . The Brigade Leader is exasperated that the Doctor is still continuing with that story . The Doctor explains the concept of the TARDIS and the fact he could use their nuclear reactor to get it working . He explains that in his world the drilling is behind schedule , and he can stop it before it takes place . The Brigade Leader wants to take a look at the TARDIS . As they leave , Doctor Williams tells him that all systems are breaking down . Once left alone , Sutton and Doctor Williams talk about when to escape . The Brigade Leader inspects the TARDIS console . The Doctor shows a few movements left over from residual energy . The Brigade Leader still doesn ' t believe . Elizabeth asks to see some proof . The Doctor drains the storage unit to travel a few seconds into the future . He asks if the Brigade Leader is satisfied . He asks if the Doctor can take anyone else with him . The Doctor says he cannot , as it will create a dimensional paradox that will shatter the space time continuum . Platoon Under Leader Benton is still keeping the resistance security forces in line despite the explosions around them . As Doctor Williams is working , a voice calls to her over the tannoy . She finds Sutton , who hears it too . The Brigade Leader , Elizabeth and the Doctor join them to hear the voice of the Director asking Doctor Williams to raise the heat shield as the manual controls are jammed . Doctor Williams goes to do this . The Doctor tries to stop her , but the Brigade Leader draws his gun and allows her to do so . The heat shield opens half way , and a figure in a protective suit pulls it the rest of the way . He pulls off the helmet to reveal the animalised human . He is joined by a fleet of others . They are not attacking , as they are acclimatising to the change in heat . Everyone tries to escape , but they are stopped by the creatures . Platoon Under Leader Benton enters and is immediately seized on . One of the creatures touches his face , and he screams and falls to the ground . The Doctor pulls some wires out of the computer , and the door closes . This creates a distraction to allow them to escape into the office . Sutton wants to save Platoon Under Leader Benton , but the Doctor forbids it . Platoon Under Leader Benton staggers around in pain as he begins to turn into one of the creatures . Sutton is dismayed that he was not allowed to save Platoon Under Leader Benton . The Doctor says that nothing could have been done as the heat would have sped up has change into one of the creatures ; that is why he closed the heat shield . The Brigade Leader and Elizabeth tell Doctor Williams about the Doctor ' s " spacecraft " . In the Doctor ' s original universe , Sir Keith is on the way back from the ministry when he notices he is being taken a different route . The driver informs him that there is traffic . Sir Keith tries the car phone . It is not working . Sir Keith tells the driver that the minister has suspended the drilling pending a full review . Sir Keith begins to get suspicious of the driver , and he eventually confesses that the Professor ordered him to take the long route home and pretend to break down . Sir Keith asks the driver to return to the complex . As he does the pair are involved in a car accident . In the parallel universe , the creatures are clawing at the office door . Inside they are all discussing the revelations about the Doctor . They all believe him , with the exception of the Brigade Leader . The Doctor says he has a plan to get out of the office but is interrupted by one of the creatures breaking through the glass in the door . Episode 6 . The Doctor uses a fire extinguisher to push the animalised humans back . The Doctor needs ten minutes to execute his plan to connect the TARDIS to the nuclear reactor . Doctor Williams questions if there is any power running through the system . The Doctor checks the air conditioning system — it is working . Doctor Williams says it must have been switched to robot control ; she would need to boost the output by resetting the emergency control , but the master switch in the next room needs to be fixed first . Sutton suddenly remembers that there is a huge amount of coolant in the adjacent room which they can use to hold off the creatures . The creatures break through , and they immediately put the plan into action . The Brigade Leader holds back the creatures with the fire extinguisher , while Sutton tries to access the coolant . The hose to the coolant has seized up , and the Doctor has to help . The Brigade Leader is surrounded , and his fire extinguisher has dried up . Just in time , Sutton has the coolant working and forces the creatures back . Sutton and the Doctor decide to stay and fix the master switch . Once outside , the Brigade Leader wants to abandon the Doctor and Sutton . Elizabeth and Doctor Williams say they intend to stay . The Doctor tells Sutton that he can go if he wants , but he refuses . Sutton asks the Doctor how he will convince them to stop drilling in his own universe . The Doctor says he may be able to convince Sir Keith . Sutton says he is dead , and the Doctor says he may still be alive in his own universe . Back in the Doctor ' s original universe , the Brigadier receives a phone call saying that Sir Keith has disappeared . Benton enters and says that the Professor is refusing to see the Brigadier and has insulted him . The Brigadier loses his temper with Benton and tells him to tell the Professor he doesn ' t have a choice . Liz is in the Doctor ' s hut , flicking switches to attempt to return the Doctor to his original timeline . The door rattles . Liz checks who it is and opens the door to reveal Sutton . He is curious what has happened to the Doctor , seeing as nobody saw him leave . He thinks that the Doctor blew himself up and that everyone is covering it up . Liz explains that there was some kind of accident but won ' t be drawn on any other details . Sutton tells Liz about Sir Keith . The Professor rails against the Brigadier . The Brigadier tells the Professor of the disappearance of Sir Keith . The Professor suggests an accident . The Brigadier says there has been no report of an accident . The Professor suggests that he might not have heard what he wanted to hear from the minister and may have taken himself off . The Brigadier says that , due to not having heard from the minister , he thinks that penetration zero should be delayed due to Sir Keith ' s objections . The Professor refuses . In the parallel universe , Sutton is still holding off the animalised humans . The Doctor has fixed the master switch . Sutton clears a path with the coolant , and they both escape , grabbing fire extinguishers as they go . Doctor Williams sees the Doctor and Sutton emerge . They all run off . Soon Bessie pulls up at the Control Centre . Doctor Williams immediately sets about fixing the computer . The Doctor and Sutton set off to get tools and cable . As they do , they feel the tremors of a distant earthquake . They head off to Bessie . The animalised humans start emerging from the complex due to the fact it is warm enough outside for them now . The Brigade Leader loses his temper at Doctor Williams , telling her to hurry up . Doctor Williams informs him that his shouting at her isn ' t helping . Elizabeth sides with Doctor Williams . The Brigade Leader explains that he has no intention of letting the Doctor escape alone . The complex is now covered with the animalised humans . The Doctor and Sutton have got back to the hut . Sutton is underwhelmed by the console . The Doctor asks him to fix the connector to the cable . Sutton warns him that if the entire output of the nuclear reactor is run through the cable , it will only last a few seconds . The Doctor assures him that that is all he will need . The Brigade Leader asks Doctor Williams how much longer she will be . She says that there is a problem with the relay circuits , and she is attempting a double bypass . The Brigade Leader loses his temper again . Elizabeth turns on him . The Brigade Leader says he plans to hijack the TARDIS , and if the Doctor refuses to be persuaded , he will kill him . Sutton implores the Doctor to make sure he stops them from drilling and connects the cable . He says that , with luck , it should work . The Doctor says they don ' t need luck but skill . Doctor Williams thinks she is ready . She pulls the lever and nothing happens . She says there must be a fault . The Brigade Leader is furious for her wasting their time . She says she will try again , but it will involve re - wiring the whole system . Sutton and the Doctor are waiting for the circuit to be complete . Sutton says that , if those explosions reach the nuclear reactor , they are all done for . The Brigade Leader watches the shaft split open . The animalised Director enters . Doctor Williams and Elizabeth run out . The Brigade Leader shoots the animalised Director repeatedly until he falls to the ground . All three of them run off , pursued by the creatures . They are sporadically thrown to the ground by earthquakes . Back at the hut , Sutton is impatient , but the Doctor is resigned to the plan having not worked . Sutton sees the trio coming . Doctor Williams apologises for the plan not having worked . The Doctor says it is fine . The Brigade Leader is furious and says it is far from fine . Sutton and the Brigade Leader argue . The Brigade Leader pulls his gun on him . Sutton says he will be only speeding up his death . The Brigade Leader pulls the trigger , but there are no bullets in the gun . The pair fight . The Doctor makes them stop , saying that they don ' t want to end their lives fighting like animals . They notice that Doctor Williams has gone back to the Control Centre to try to remedy the situation . Sutton goes to help her . Doctor Williams is re - wiring the computer when Sutton enters , furious . She asks what any risk to herself matters . The animalised Director awakes , and Sutton attacks it with a fire extinguisher . As he does , Doctor Williams gets the circuit working . They run to the hut . Elizabeth notices that the console is working . The Doctor says it is gaining power rapidly . The Brigade Leader pulls his gun and orders him to take them with him . He fires the gun in the air to prove it now has bullets in . The Doctor says he wants to but can ' t as it will cause a cosmic disaster . The Doctor says that the Brigade Leader is going to have to shoot him . A gunshot sounds in the hut , but it is the Brigade Leader that falls to the floor . The other three implore the Doctor to leave . A huge explosion shakes the complex . Lava begins to flow from where the drill shaft was . Men and animalised humans run in terror . The Doctor says he cannot dematerialise as the power is too erratic . Lava begins to encroach through the door of the hut . Episode 7 . The Doctor is prostrate and unconscious on the floor of the hut . He is discovered by Liz , who calls for Benton to fetch the Brigadier . It is three hours and twenty two minutes until the drill reaches the centre of the Earth . The Professor gives orders to boost the drilling . Petra is unsure as to the safety , but the Professor orders it . Petra tells Sutton , who wants to confront the Professor , but Petra stops him , saying that she will try first . Benton tells the Brigadier about the return of the Doctor . Sutton overhears . The Professor will not listen to Petra . He is strongly affected by a noise that emerges from the drill . Petra is worried for his health , but he says he merely has a headache . Sutton tries to persuade the Professor . Again he is blocked , and again the noise has an effect on the Professor . The Professor storms off , leaving Petra and Sutton worried about his mental health . Liz is checking the Doctor ' s health . All is fine , and he is just in some kind of coma . The Brigadier wants to fetch a doctor , but Liz blocks him . Sutton warns the Professor of an issue with the number two output pipe . The Professor ignores him . Sutton loses his temper , and the Professor says that if he is so worried , he should leave . Sutton goes to leave when Petra stops him . Sutton tries to convince her to come with him , but she says she can ' t . They are interrupted by an explosion from the drill head . The Brigadier is informed of the issue . The Doctor stirs . He mutters that the number two output pipe has blown . The Brigadier is stunned , as he has only just heard that information himself . Still in his coma , the Doctor mutters , " Reverse all systems immediately " , before slipping back into unconsciousness . Liz goes to Central Command to tell them what the Doctor said . The Professor is struggling to keep everyone in their positions and is refusing to stop the drilling . Liz enters and asks Sutton and Petra what would happen if they reversed the systems . Sutton says it is not a bad idea . Petra says they would never get the Professor to agree . Liz says they should just do it . They all rush off . The Doctor stirs in his coma . It has worked . Liz says it was the Doctor ' s idea . The Professor is angry at Petra for having not run the plan past him . The Doctor awakens to the Brigadier and Liz . He tells the Brigadier he looks better with a moustache . He checks his pulse and is healthy . He tells Liz and the Brigadier where he has been . They think he is still delirious . He asks the Brigadier , who he calls the Brigade Leader , if they have caught the animalised scientist , whether the Professor seems ill and the state of the drilling . There is a knocking at the door . It is Sir Keith . The Doctor is overjoyed to see he has survived his accident . Sir Keith tells the Brigadier that the Professor is going to face some serious charges . The Doctor has realised that with an infinity of universes comes an infinity of choices , free will is not an illusion and patterns can be changed . The Doctor stops the Brigadier from calling a doctor for him and tells Sir Keith what is going to happen . The Doctor bursts into Central Command and says that drilling must be stopped . The Professor orders the Brigadier to arrest him . The Doctor rushes to a computer and destroys it . The Brigadier pulls him away and orders him to be taken to the sick bay . Sir Keith confronts the Professor . The Professor says he has no intention of going to see the minister until after drilling is complete . Petra tells the Professor that they will be switching to robot controls in forty nine minutes . The Professor says he feels cold and orders her to increase the temperature . He has some kind of fit that causes the scientists to look at him in shock . He orders them all to leave the area as he will finish the procedure alone . Sutton and Petra are shocked as to what the Professor is doing . The Professor closes the heat shield . The Doctor uses karate to elude his guards before running off and hiding . The guards come to and run past him in his hiding place . The Doctor is approached by the animalised scientist . He neutralises him with a fire extinguisher . The Professor studies the green goo that is dripping out of the drill head . He rubs his hands and face with it before falling to the ground . Petra hears the cries of the Professor through the tannoy and is concerned for the Doctor . Sutton tells Sir Keith that they cannot access him as he has locked the heat shield from the inside . Behind the heat shield , the Professor is fully animalised . The computer is advising that the drilling should be stopped . The Doctor re - enters just as the heat shield rises and the animalised Professor emerges . The Professor attacks the Doctor with a chair , but he and Sutton neutralise him with fire extinguishers . The Doctor orders that the drilling be stopped . Sutton says that they should cut off the power . Petra warns that this would cause the drill to disintegrate ; Sutton says that would be for the best . Petra stops the drilling , but it continues . Sir Keith warns of the buffer controls , which cause the drill to slow rather than stop dead . This means the drilling will continue for five minutes — long enough for the drill to reach the centre of the Earth . The Doctor and Sutton run off and discover the server switches have been smashed . With one minute left , the Doctor begins to tamper with the switch . Everyone looks on , worried . With thirty five seconds left , the Doctor and Sutton return , having stopped the drilling for good . Liz hugs the Doctor . The Doctor says that the shaft should be filled in immediately . Back in the hut , the Doctor and Liz are working on the TARDIS console . There is a knocking at the door . It is Sir Keith , accompanied by the Brigadier . He has come to say goodbye . Sir Keith says everyone is leaving as the project has been abandoned . The Doctor is told that he has one more day with the nuclear reactor before it is dismantled . Sir Keith also informs them all that Sutton and Petra left together . Once alone , Liz and the Brigadier ask why the Doctor still wants to use the nuclear reactor . The Doctor says that the console is now fully functional , and he can use it at will . The Brigadier scoffs at him , and the Doctor says he reminds him of the Brigade Leader . He bids goodbye to Liz before saying that he cannot stand another moment with the Brigadier , whom he describes as a pompous , self - opinionated idiot . He flicks a few switches and disappears . Liz turns to the Brigadier , cross that he has forced the Doctor to leave . There is a cough at the door . A rather bedraggled looking Doctor stands at the door . He informs them he moved a few seconds forward in time and just left into a rubbish heap . The Doctor tries to smooth over his cross words to the Brigadier in an effort to get some UNIT soldiers to return his console . Home video and audio releases . DVD releases . This story was released as " Doctor Who : Inferno " . Released : Contents : Notes : DVD special edition . " Inferno " has been re - released as a special edition in 2013 . Digital releases . This story is available : Video release . This was released as a double - cassette pack on VHS in the UK in episodic format in March 1994 , including in episode five the scene not shown on the original UK transmission ( see " DVD releases " above ) .