The Green Death ( TV story ) The Green Death was the fifth and final story of the " Doctor Who " tenth season . The story marked the departure of companion Jo Grant , played by Katy Manning . It also bore witness to a series of traumatic events for Captain Mike Yates and made him doubt his faith in humanity , which deeply upset him . His inability to deal with his doubts later led him to a path of rebellion . Synopsis . A death at an abandoned coal pit brings UNIT and the Third Doctor to the South Wales town of Llanfairfach when the body is found glowing bright green . Are pollutants from Global Chemicals responsible ? Where are the giant maggot s coming from ? And who is the mysterious BOSS ? Plot . Episode 1 . In the Glamorgan county Llanfairfach , a colliery remains inactive after the post - industrial closure of its mining operations . A miner visits one of the underground roadways for inspection . He is scared by a green substance which has infected him during his stay beneath the surface , and he darts for the lift . Meanwhile , a Range Rover arrives at a crowd of deposed workers formerly employed at the mining facility . A man steps out and addresses several miners . His company is introducing a new process that will greatly expedite their production of oil after the National Coal Board had to close down the pit because of coal ' s dwindling industrial promises . The workers cheer vigourously but are met with the sickened remarks from a band of protesters . One of them is a prolific troublemaker in these parts — Professor Clifford Jones , who believes the men are being exploited for their manpower . The workers are far from rapport toward his unpleasant words and start jeering at him to shut up . Instead , all voices are unanimously silenced by the sound of a warning whistle bellowing without stop . The miners know this means there is trouble at the pit , rushing off where an emergency awaits . The same mining worker has emerged from the shafts , collapsed dead with his hand wrenched firmly on the valve to blow the whistle . His flesh has been contaminated by a phosphorescent green substance . The Welsh mining village of Llanfairfach is of little interest to the Third Doctor , who would rather take a challenging visit to the blue planet of Metebelis III than a trip to South Wales . However , Jo Grant reads a startling newspaper article about a corporate facility that is gearing up to cause a huge amount of pollution . She is keen to go to the village to meet the acclaimed environmentalist and Nobel Prize winner Professor Clifford Jones . Brigadier Lethbridge - Stewart arrives and tries to assign a murder investigation mission to the Doctor and Jo , but the Doctor firmly tells him no repeatedly , as he wants to be off to Metebilis III . Jo pleads her case with the Brigadier over the events she wants to deal with firsthand , but Jo is not impressed with the Brigadier ' s siding with the corporate giant . She passionately protests that she would even quit UNIT if it interfered with her ability to go there firsthand . Luckily , Lethbridge - Stewart ' s mission was to visit the facility — he is intrigued enough by the death of a bright green miner to drive her down . The miner was found in a disused mine , and the main source of employment in the village is now the Global Chemicals petroleum factory . Its boss , Stevens , promises prosperity for all , but Professor Jones and the other environmentalists at his " Nuthutch " are unconvinced . In light of the protests , Stevens accepts the Brigadier ' s offer of additional security at his factory . Stevens , however , is told by a voice that " nobody must go down the mine " and zones out , muttering these words to himself when he speaks to his employee Hinks . When Hinks leaves his office , Stevens unsheathes a pair of large headphones and plugs them into a machine . An unusual sound begins whirring into his head . Jo discovers the Nuthutch , home of the workshop where Professor Jones is engaged in eco - friendly exploits , but is taken aback by a strange fellow who welcomes his guest with eccentricities , micromanagement , and a patronising attitude toward her . Annoyed with this person , she gives him a what - for , causing the man to lighten up and calm Jo down so she stops bumping into things inside an already crowded room . He shows Jo a new type of fungus that Nancy has been developing , " Saliota Orbis " . It is supposed to be a safe alternative to protein - rich meats . Jo figures out this man is really Professor Jones , and gets on well with him . Professor Jones detracts the operations Global Chemicals is running , noting that " it ' s still using up the oil and doubling the atmospheric pollution . " He suggests cleaner alternatives that harness the energy with which the sun provides them , such as wind power and water power . Jones explains the Nuthutch has natural heating tapped from the river , through a heat pump working on electricity generated by a windmill . Jo learns the logic behind his use of alternative technology : no waste or pollution . Jones goes on to hypothesise that Steven ' s oil manufacturing process " must be based on Bateson ' s polymerisation , and that means thousands of gallons of waste . Aye , a thick sludge you can ' t break down in any way , like a liquid plastic . And what properties that would have , heaven alone knows . " The professor wants to know what they ' re doing with that waste , thinking it was possibly connected to Hughes ' death . Jo figures Global Chemicals could be pumping the waste down the old mine workings and suggests the two of them should go explore it . Jones doesn ' t seem to get the picture , and Jo insists they visit the mine now . Unfortunately , Jones ' s abrasiveness gets the better of her when he calls her a child and says he has work to do . She storms out of his workshop , slamming the door on her way out . Unbeknownst to the Doctor and Lethbridge - Stewart , Jo decides to venture down to the mine by herself , accompanied by a friendly miner called Bert . The Brigadier still arrives to investigate the death , suspicious about Elgin ' s testimonial regarding their outstandingly clean and efficient oil production . He begins to grow weary after patching several calls to UNIT headquarters with no reply . The Doctor has weathered a violent excursion on Metebilis III and returns in his TARDIS with a torn jacket and dirt on his face . He finally answers the call after being derelict and rushes to Global Chemicals in Bessie , suited up in new clothes . Once the Brigadier has explained the situation to his colleague , the Doctor orders that no one should go down the mine until he has personally inspected it . However , Jo has already gone down with Bert to aid another miner with her first aid skills . The man who went down before them was Dai Evans , wanting to figure out what killed the miner who died pulling the emergency whistle for the shaft and was found glowing green . Now , he is starting to glow in the same way and has called for help . The Brigadier and Doctor notice the mine shaft lowering mechanisms spinning from outside and bolt into the facility to stop the descent , upset that it ' s Jo who has gone down before him . Even when the Doctor demands that Dave , the shaft operator , raises Jo and Bert back up , Dave can ' t get the brakes to work . One of the Global Chemicals employees cuts the lift cable and they plummet towards the bottom of the mineshaft . . . Episode 2 . The Doctor reaches Llanfairfach with a blue crystal to show for his visit to Metebelis III and jams the lift in the nick of time . Jo and Bert are not harmed , but they are stranded in the mine . There , they find Dai Evans , one of the other miners , glowing bright green and terribly ill . It seems there is some serious pollution at work in the mine , and they head off to find a way out . For anybody to get down to the mine to help them , cutting equipment is needed to cut the cables jamming the lift . Global Chemicals say they don ' t have any such equipment , but a staff member , Elgin , knows this is not true . When Jones hears about Jo ' s predicament , he comes to the mine to help . The Doctor sneaks into Global Chemicals to steal the equipment , but he is caught . One guard sees him as a bit old for a threat , but the Doctor jests , " I ' m quite spry for my age , actually . " It doesn ' t take him much effort to knock the guns out of his hands and properly throw several guards to the ground with his Venusian aikido , not fazed by their use of a baton . He takes the upper hand until four more arrive , this time armed with rifles , and fence him in . Fortunately , Stevens chooses to overlook the incident . By chance , the Brigadier finds somebody with cutting equipment in a garage , allowing the Doctor and a few mine workers to go down into the mine shaft . Things get worse when Bert finds a slick of green slime and touches it . He too seems to contract " the green death " . By the time the Doctor finds Dai , the miner is dead , and the Time Lord becomes very worried for Jo ' s safety . Increasingly ill , Bert waits behind while Jo looks for a way out alone . The Doctor catches up with Bert and finds Jo near a vast lake of green slime filled with giant maggots . When they try to go back , the tunnel caves in and more maggots emerge from the rubble . Episode 3 . The Doctor and Jo are trapped between a cave - in and the pool of maggots . They escape by wheeling a mine cart through the maggots , but they are still trapped in the mine . Back at Global Chemicals , Stevens is behaving very curiously . He is using strange headphones to listen to calming messages , and when one of his employees , Ralph Fell , looks helpful to the environmentalists , he is somehow reconditioned with the same headphones and shortly afterward kills himself . Elgin saves the Doctor and Jo from drowning in the green slime when he helps them out of a shaft that links the mine and the factory complex — proving the link between the two . The Brigadier ' s plan to investigate Global Chemicals further is cut short when he is ordered by the Prime Minister himself to let Stevens get on with it . Stevens evidently enjoys Cabinet support for his factory and its new plastic production process . The Doctor , Jo and the Brigadier end the day with a nourishing meal of fungus at the Nuthutch , but the frivolity is cut short when they hear Bert too has died . As the Doctor leaves , a maggot egg he brought back from the mine hatches , and the maggot inside creeps up on Jo , the girl none the wiser . Episode 4 . The maggot kills Hinks , who had come to destroy the egg , and escapes before any analysis can be made of it , leaving the Doctor and Jones to analyse the trail of green slime it left behind . The Brigadier receives orders to seal the mine with explosives and clear the area using UNIT troops . The Doctor realises that this will only make the situation worse , but his plea to Stevens to allow an investigation is ignored . As the Doctor expected , the maggots simply burrow through and are now a threat above ground . Not to be intimidated by Stevens , the Brigadier sends Captain Yates into Global Chemicals , undercover as a Ministry official . The Doctor dons some improbable disguises , including a milkman and a cleaning lady , to get through the gates and move freely . Meanwhile , Jo has alienated Cliff , with whom she is falling in love , by ruining one of his slides . Determined to make amends , she heads to the sealed mine in search of a maggot to run some tests on . Having liaised with Yates , the Doctor learns that Stevens takes his instructions from the top floor of the complex , and heads there to find out who is in charge . The BOSS , or Biomorphic Organisational Systems Supervisor , turns out to be a supercomputer with its own megalomaniacal personality . Episode 5 . The Doctor speaks with BOSS and finds out that it runs the company , controls Stevens and other key staff members , and is responsible for the polluting chemical process . The Doctor employs the liar paradox , a conundrum which will keep BOSS busy trying to find a solution , while he escapes . Unfortunately , he runs into Stevens and some guards before he can do so . He rejects the brain - washing technique that Stevens subjects him to , but Mike Yates is more susceptible and is converted into one of the computer ' s slaves . After the Doctor escapes , Mike is sent to the Nutchutch to kill the Doctor . His conditioning is deep and only broken by the Doctor ' s use of the blue crystal he brought from Metebelis 3 . Meanwhile , Jones has worked out that the fungus Jo spilt on the slides is actually a curative and then sets off to stop her , but they are both caught in an RAF bombing raid intended to kill the maggots . Cliff is also infected with a maggot and begins to turn green — before he was able to share his knowledge of the cure . In a delirious state , he utters the word " serendipity " . Yates re - enters Global Chemicals , pretending to still be under BOSS ' s control , but he is caught by Stevens , who tells him he just can ' t depend on anyone . Episode 6 . Sergeant Benton brings an empty maggot chrysalis to the Nuthatch , revealing that the maggots are about to change into something else . The Doctor discovers that another maggot had died after eating Cliff ' s fungus , meaning that it is deadly to them . The Doctor and Benton drive around the slag heaps and the mine , liberally scattering the fungus which kills all the maggots , and disposing of a deadly giant fly which attacks them . Returning to the Nuthatch , the Doctor discovers Cliff ' s cure and uses it to restore him to full health . The Doctor then returns to Global Chemicals to confront BOSS . The computer plans to link up with others and effect a corporate takeover of the human race . However , Stevens , whose conditioning is partially broken by the Doctor using the crystal , tells him to get out while he triggers an explosion which destroys himself , the computer , and the company headquarters . The menace defeated , UNIT troops and environmentalists gather at the Nuthutch for a celebration made all the more special when Jo and Cliff announce they are getting married and then plan to travel the Amazon looking for a rare fungus , and that the United Nations ( after Jo contacted her uncle ) have decided to fund Wholeweal ' s research : jobs will return to Llanfairfach after all . The Doctor offers his blessing to the couple and gives Jo the blue crystal as a present , asking them to save him some wedding cake . However , as the party starts to get into full swing the Doctor quietly slips away , noticed only by Jo , who understands why . The Doctor , upset by the departure of his good friend , gets into Bessie and , after one final look back at the cottage , sadly drives away . Jo and Cliff kiss , enjoying a tender embrace , while the heartbroken Doctor drives off into the sunset . Home video and audio releases . DVD releases . This story was released as " Doctor Who : The Green Death " . Released : Contents : Notes : Special Edition . As with many pre - 2006 releases , " The Green Death : Special Edition " was released on 5 August 2013 . Doctor Who DVD Files . It was released as issue 48 of " Doctor Who DVD Files " . Digital releases . This story is available : Video releases . Released as " Doctor Who : The Green Death " , the two - cassette video release was rushed out in memory of Jon Pertwee , who had passed away earlier in the year . Released :