Four to Doomsday ( TV story ) Four to Doomsday was the second story in the nineteenth season of " Doctor Who " . It was the first story filmed with Peter Davison as the Fifth Doctor . Much like with " Castrovalva " , Adric is seen apparently siding with the main enemy of the story ; in this case by telling Monarch invaluable information about the Doctor , the Time Lord s and the TARDIS . At first it seemed like a straightforward betrayal , but Adric had in fact been tricked into thinking Monarch was harmless to them ; he later saw the error of his ways . Synopsis . The Fifth Doctor , Nyssa , Tegan and Adric arrive on a spaceship which is headed for Earth . On board they meet natives of Earth from various different eras , and also three Urbankan s : Monarch , Persuasion and Enlightenment . What are the aliens ' intentions when they reach Earth ? Plot . Part one . The Doctor tries to return Tegan to Heathrow Airport , but the TARDIS lands on a technologically advanced ship . The Doctor goes out to investigate and sees a monopticon surveying them . He returns to the TARDIS and emerges with Adric , Nyssa and Tegan . All four must wear helmets to breathe . The Doctor addresses the monopticon , hoping whoever is using it for surveillance will see they are friendly . He queries it on their location . A door opens . Seeing this as a friendly gesture , the Doctor goes through it , followed by Tegan . Nyssa and Adric stay in the room to operate some machinery there . Tegan and the Doctor eventually find themselves on the ship ' s bridge and meet the Monarch and his two associates , Enlightenment and Persuasion . The Monarch is interested in the Doctor and Tegan ' s knowledge of current and past Earth culture . He reveals the ship is bound for Earth . Tegan draws a picture of male and female uniforms at Heathrow for Enlightenment . Tegan and the Doctor leave the bridge and meet up with Nyssa and Adric . Nyssa claims she saw a humanoid man . The Doctor doubts this until one emerges , dressed in a Greek toga , to ask them to follow him . They are led to a dining chamber and seated at a table , to be joined by an Aborigine ( Kurkutji ) , a Mayan ( Villagra ) and a Chinese mandarin ( Lin Futu ) . They are representatives of their respective cultures ; the Greek ( Bigon ) represents ancient Greece . The last guests to join them are Enlightenment and Persuasion , who have transformed into the humans Tegan sketched . Part two . The TARDIS crew are reunited as guests aboard the ship . It soon becomes apparent there are four distinct human cultures represented by a small group of humans : Ancient Greeks , the leader of whom is the philosopher Bigon ; Chinese Mandarins and their leader Lin Futu ; Princess Villagra and representatives of the Mayan people ; and Kurkutji and his tribesmen , of the Australian Aboriginal culture . The Urbankans have visited Earth , each time getting speedier in their journeys . This time they have left their homeworld after erratic solar activity , storing three billion of their species on slides aboard their craft . It seems the current journey is their last and they wish to settle on Earth , which they are due to reach in four days . Bigon demonstrates to an astonished Doctor that within his chest and beneath his face there is just a mass of electronics . Holding up a printed circuit connected to his chest , he states : " This is me . . . " Part three . The Doctor becomes suspicious of the Monarch . He learns the Urbankans don ' t plan on a peaceful co - existence with humans . Instead , they will use a toxin that the Urbankans produced from their own bodies during the " flesh time " before they were converted to androids , which causes organic matter to shrink away to nothing . It will be unleashed before the Urbankans disembark . Adric and the Monarch have a conversation about the Doctor and his TARDIS . Adric tells Monarch about the TARDIS and Adric goes off to ask the Doctor if Monarch could be allowed entry to the TARDIS . Nyssa is held back by some androids The Doctor discovers the humans aboard are not descendants of the original abductees . The original people were taken from Earth and converted into androids , just like the three Urbankans . This revelation causes a panicked Tegan to use a spare key to get into the TARDIS , and she tries to pilot it back to Earth , but only succeeds in materialising it in space next to Monarch ' s ship . Enlightenment hypnotises Nyssa and tells her to recall all past life . She is then taken by the androids to be processed . They take Nyssa to the Mobiliary and she is put into a machine to turn her into an android . The four leaders have been given additional circuits to help them reason , but this faculty can be taken away , as Bigon learns when he crosses Monarch once too often . He explained to the Doctor that Monarch strip - mined and destroyed Urbanka in a quest for minerals to improve the ship , and now plans to do the same to Earth . Monarch believes that if he can move the ship faster than the speed of light , he can pilot it back to the beginning of time and discover himself as God . Adric is restrained as , on Persuasion ' s orders , the Doctor is forced to his knees and one of the Greek androids raises a sword to decapitate him . . . Part four . Nyssa uses the Doctor ' s sonic screwdriver and a pencil to short out the androids and save his life . Adric stops Persuasion from shooting the Doctor by standing in the way and the Monarch announces the Doctor is not to be harmed . Despite these events , Adric is taken with Monarch , and relations between the Doctor and him become very strained . It takes the truth to break the alien ' s hold over the boy . The Doctor sets about overthrowing Monarch and , with the help of the human androids led by a restored Bigon , a revolution begins . The Doctor is forced to go out into space in order to retrieve the TARDIS , but Persuasion attempts to stop them . The Doctor and Adric tear out Persuasion ' s circuit and throw it into space . Enlightenment then tries to stop them and stuns Adric before the Doctor is able to get back into the TARDIS . Adric recovers after Enlightenment strands Doctor in space and tears out Enlightenment ' s circuit . The Doctor uses his cricket ball to propel himself the rest of the way to the TARDIS . The Doctor then lands the TARDIS back on the ship . Monarch tries to kill the TARDIS travellers by shutting down life support , but they are able to survive with the help of the helmets they brought from the TARDIS . The Doctor retrieves a sample of the Urbankan toxin , intending to analyse it and turn it against its creator , but when an armed Monarch confronts the Doctor , he ' s forced to use the entire sample against Monarch , who is reduced to just inches tall . It seems he is a product of the weak “ flesh time ” after all , having never , as the Doctor suspected , been fully converted into an android . Adding insult to injury , the Doctor reveals that Monarch ' s plan to travel back in time was ridiculous , and would never have worked . With their former ruler now captive and helpless , the humanoid androids decide to pilot the vessel to a new home on a new world , while the TARDIS crew departs . Back in the console room , Nyssa collapses to the floor in a dead faint . . . Home video and audio releases . DVD releases . Notes : Special features : Video releases . This story was released in the United Kingdom and Australian markets in 2001 and the US market in 2002 .