The Ark ( TV story ) The Ark was the sixth story in the third season of " Doctor Who " . It was the first full serial for new companion Dodo Chaplet , who had appeared only briefly at the end of the previous episode . It was also the first to take place in what was definitively humanity ' s far future , and the first to depict the demise of Earth . Behind the scenes , it was notable for its then - groundbreaking use of out - of - sequence recording . The final episode , " The Bomb " , was the first in " Doctor Who " history to be recorded according to set availability and then edited into proper sequence . ( DCOM : " The Bomb " ) Director Michael Imison also notably achieved a number of special effects shots through the liberal use of , something which hadn ' t been widely attempted in " Doctor Who " to that time . Imison ' s use of playback to indicate that the bridge computers and control consoles on the " Ark " were fully operational was also unusually sophisticated for the Hartnell era . " The Ark " was also the first time a female writer was credited on the show , though the extent of Lesley Scott ' s contribution was rather small . ( " About Time 1 " ) Michael Sheard and Roy Skelton had their first involvement in " Doctor Who " with this serial , with the former appearing five more times and the latter going on to voice the Dalek Emperor , the Cybermen and , briefly , K9 . Synopsis . The Doctor and his companion s Steven Taylor and Dodo Chaplet arrive some ten million years into the future , on board a generation starship which is carrying the last of humanity away from an Earth that is about to fall into the Sun . However , the cold that Dodo has could prove devastating to these future humans and their servants , the Monoid s . Plot . The Steel Sky ( 1 ) . As the TARDIS materialises in a tropical rainforest , a one eyed alien watches it in curiosity . Dodo emerges and immediately sneezes before going out to explore . Steven follows after her , confused as to her bravery . Dodo seems convinced that she is in Whipsnade Zoo and points out a number of Earth creatures , such as a chameleon and other lizard s , to back up her point . The Doctor seems to back up her point by saying that all readings say that this planet has similar conditions to Earth . Elsewhere a court has met , populated by humans and the alien race , the Monoid s . They are putting on trial a member of the human race that put the whole of their civilisation at risk . Despite pleading from the Commander ' s daughter , Mellium , the Commander sentences the man to miniaturisation for 700 years . The man is led into a device that shrinks him down into a microcell and he is carried away . Back in the jungle Dodo finds an elephant and uses this to prove that they must be on Earth , but the Doctor points out that all of these animals are not indigenous to the same area . He also points out other anomalies that he has discovered since their landing . One is that there is no sky , just a metal roof over them , and the other is that the ground is rumbling as if mechanised . All this time the Monoid still watches over them . Back at civilisation Zentos , a sceptical young understudy to the Commander , receives information from one of the Monoids , who communicate through sign language , that there are intruders on the ship . When he feeds this back to the Commander he doubts it , but there is incontrovertible video proof . Zentos suggests they are immediately arrested and questioned . The Commander agrees to the questioning but says that they should be invited . As the Doctor and his companions explore , they hear an alarm raised and discover that the Monoids are exploring the TARDIS . They rush into a nearby cave where they avoid detection , despite Dodo ' s sneezing almost giving them away . The Doctor berates her , but she explains she is coming down with a cold . Once the coast is clear , the Doctor and his companions go out and explore . As they mount the crest of a hill , they see a city off in the distance . The Doctor immediately knows where he is now and explains that they are on a giant spaceship . As he does they are immediately surrounded by small human - like figures . The Doctor and his companions are led to the city where they are cross - examined hostilely by Zentos , whilst the Commander welcomes them with curiosity . The Commander explains that the Monoids are a peaceful breed of alien who came to Earth from their own planet which was dying . They helped the human race to build this ship to escape Earth , which was itself dying due to the solar flares that were engulfing the planet . The Monoids also taught the humans the miniaturisation process which allowed the whole human race to be transported to their destination , Refusis II , and brought back when they arrive in 700 years time . The Doctor suggests that this means they have travelled nearly 10 million years into Earth ' s history . The Commander allows the Doctor and his friends the run of the ship . Steven and Dodo are led away by Mirian to be shown a statue , whilst the Doctor is shown the technology of the ship . Zentos is still sceptical of the Doctor ' s story , suggesting that he may be a Refusian come to scupper the ship ' s progress to Refusis II . Mirian shows Steven and Dodo the giant statue of a Homo Sapiens that they are constructing out of gregarian rock , but the tour is interrupted by another alarm . They return to the main deck of the ship and see a Monoid laid out on a gurney with a fever and illness . As they flock round the alien , the Commander also starts to complain of a severe fever and falls to the ground . Zentos overhears a conversation between the Doctor and Steven wherein he explains that this is down to Dodo ' s cold . The humans from the 57th segment of time have no resistance to diseases so even the common cold could kill them . Zentos rushes to a podium and claims that it is Dodo that has started to spread this disease . As he talks , the Monoid dies . The humans are in a fervour of excitement and shock , and the Doctor and his companions are arrested and led away . The Plague ( 2 ) . The Doctor and his companions are locked away in a prison cell . Steven questions the Doctor as to whether they have ever contaminated anywhere else before in their travels . The Doctor admits that it is something that he has never considered before . Back in the control room Zentos is getting evermore panicked as more and more Monoids die whilst greater numbers of the human population are becoming ill . The doctor of the ship confides to Mellium that he is at a loss for a cure for the Commander . In the prison the Doctor and his companions overhear the burial of a Monoid — which is performed by ejecting them from the spaceship . Zentos uses the funeral gathering to gain popular support for a trial of the Doctor and his companions . He employs Baccu to act as prosecutor whilst Manyak and Mellium will offer defence . Mellium informs the Doctor that one of his contingent will have to offer evidence in the trial . Steven offers himself as he is feeling hot and unwell in the prison cell . He is led into the control room where he continues to sweat and feel ever more under the weather as the trial continues . Baccu begins by accusing Steven and his friends of being Refusian and being sent to kill them . Steven denies this , but Zentos says that their own story of time travel is equally as hard to believe . Manyak offers a bargain to Zentos , saying that the only hope that the humans and the Monoids have is that the Doctor could cure them ; however , Zentos is against this and riles the crowd up into saying this will help them spread the disease more quickly and efficiently . The Commander , who is watching these proceedings from his sick bed , agrees with Manyak ' s proposal . As the jury are mulling this over , a human informs the assembly that a human has died of the illness . Zentos uses this as ammunition to sway the jury ' s verdict , and they all automatically judge the Doctor and his companions as guilty . Zentos sentences them to ejection from the ship . As this verdict is read out , Steven collapses due to his worsening condition . Steven is carried back to the prison cell , where the Doctor tries to argue his point with Zentos but has no effect . Zentos sends Baccu away to prepare the ejection , but the Commander orders Zentos , over loud speaker , that the Doctor should be freed and given the chance to cure the disease on the one exception : that Steven is used as a guinea pig first . Mellium presents herself to the Doctor to help in any way possible . He orders her to keep everyone warm whilst sending Dodo back to the TARDIS to get his equipment . The Doctor orders Baccu and Manyak to begin a hunt for certain animal membranes that he can combine to form a vaccine for the common cold . Later , when this has been extracted , the Doctor applies his vaccine to Steven before straight away applying it to the other humans , starting with the Commander . Baccu and Manyak suspect that this may not work and that Zentos is ready to eject the Doctor if it doesn ' t . After an hour Steven is showing no signs of improving . Eventually he begins to writhe in pain before falling back limp and lifeless . Dodo is concerned that he is dead , but the Doctor states he is sleeping soundly with his fever cured . Dodo and the Doctor go out into the control room and receive congratulations for their efforts . After everyone is better the Doctor and his companions are given a heroes ' farewell led by the Commander and are escorted back to the TARDIS . The TARDIS demateralises and , seemingly , materalises back again . The Doctor and his companions emerge , bemused by this . Their bemusement grows when they discover that there is no one around on the ship . The travellers are stopped in their footsteps when they discover the statue fully built — but with the head of a Monoid . The Return ( 3 ) . The Doctor deduce s that 700 years have passed since they were last on the Ark and discovers that they are close to Refusis II . The Doctor discovers that the reason why there are no humans around is because the ship is now piloted by an automatic guiding device ; however , a quick scan of the ship shows that there are some signs of life . The Doctor observes humans serving under Monoid control . As they observe this , they are caught by a Monoid , who are now able to speak and identify themselves through numerics depending on their position on the ship . Two and his personal manservant Maharis lead the Doctor and his companions to One . Before One allows the Doctor and his friends into the ship , he watches back footage from 700 years ago and watches the Doctor dematerialise . He tells the Doctor that he should thank him as the long term effects of the fever transmitted by Dodo sapped the morale of the humans and allowed the Monoids to take over . One informs the Doctor and his friends that they are to be imprisoned in the servant kitchens . Two human servants , Venussa and Dassuk , talk of the rumoured arrival of the Doctor , a figure that Dassuk puts down to myth , but he is put on his place when the Doctor arrives in his kitchen . The Doctor begins to talk about how to liberate the humans from the Monoids . Steven suggests that they overpower one , but Dassuk says this has been tried before unsuccessfully . Back in the Control Room , a Monoid grand council has been called . One informs the Monoids that they are close to Refusis II and that they will send down a party first to ensure its safety . He also informs the Monoids that the humans will not be accompanying them to their new home . After the meeting , One asks Two to fetch the Doctor and Dodo , who will make up the search party . As Two enters the kitchens , Steven and Dassuk try to overpower him but are interrupted by Three , who kills one of the humans to break up the melee . Two seizes the Doctor and Dodo and leads them away . Three informs Steven that he is being kept here as security . The Doctor , Dodo , Two and a human called Yendom are placed on a launcher and fired down to Refusis II . The planet seems both hospitable and deserted , but as the party explores an invisible figure enters the launcher and begins to toy with the controls . In a conversation with Dodo , Two lets slip that the humans will not be joining the Monoids on Refusis II . An argument breaks out that is only stopped by the Doctor , who points out a castle that lies in the distance . On closer exploration the castle is also deserted . Two begins to destroy the interior of the castle , hoping that this will draw the attention of a Refusian . A disembodied voice calls for Two to stop , but he refuses . Two is overpowered by an invisible figure who goes about setting the house in order . Back on the Ark , One explains his plan to some other Monoids . He explains that as soon as they have got to Refusis , he plans on blowing up the ship with a bomb placed inside the Monoid statue . Maharis sees this conversation over one of the video controls but isn ' t aware of where the bomb is . Maharis goes to the kitchen , where he is initially met with hostility due to the fact that he sided with the Monoids so as to avoid total servitude , but he explains to them the Monoid plan . On Refusis II the Doctor is mediating with the Refusian . The Refusian explains that the castle has been built for the Monoids as they have no purpose for them anymore — they lost their material form after a solar flare hit Refusis II . They will happily share their planet if the Monoids wish to live in peace . Outside the castle Two explains to Yendom that he is going to radio back to the Ark to explain the situation . Yendom tries to overpower Two but is killed . Two gets into the launcher and begins to feedback to the Ark on how to destroy the Refusians . Unbeknownst to him a Refusian is outside the ship and blows up the launcher , leaving the Doctor and Dodo stranded on Refusis II . The Bomb ( 4 ) . The tension of the situation ferments dissent in the Monoid ranks , with Four openly opposing One ' s plans to abandon the humans and colonise Refusis without more checks on the planet . One is informed of this plot and says he will kill Four if the dissent becomes public . Back on Refusis II , the Doctor strikes a bargain with the Refusians whereby if the humans and the Monoids can prove themselves peaceful they will live in harmony with them on the planet ; however , if they are violent they will not stand for it . The Doctor thanks them for their kindness . In the kitchen of the Ark , Steven plots a plan to escape . When Maharis comes to deliver their food , Dassuk hides . Steven distracts Maharis whilst Dassuk slips out . As soon as the coast is clear Dassuk returns and frees all the prisoners . As Steven and the prisoners are making their way to the control room , One decides that it is time to leave the ship for Refusis II after setting the bomb to go off in twelve hours . Steven and his friends arrive too late and set about scanning the ship in search of the bomb . The launchers arrive on Refusis II where One immediately claims the planet for his own and Four plots to return to the Ark as they fear danger on the planet . As soon as the Monoids are out of sight , the Doctor , Dodo and the Refusian use a launcher to contact Steven . They tell him they will send some launchers back whilst the Doctor tries to extract information from the Monoids regarding the location of the bomb . The Refusians are tasked with piloting the launchers back to the Ark whilst the Doctor and Dodo leave , only to be captured seconds later by Three . Three watches in amazement as the launcher takes off with no one in it . When the Doctor is brought to One he tells him , in all honesty , that he has never seen a Refusian so can ' t help him . One threatens the Doctor ' s life unless he starts to be more helpful . This impasse is broken up by Four ' s challenge to One . Four issues a speech whereby he says that he is returning to the Ark and any true Monoid will join him . In this conversation , One lets slip the location of the bomb in the statue . A number of Monoids leave with Four . As soon as he is gone , One states that he is going to follow them and spring an attack on them . On the Ark the launchers have returned , and the humans are surprised to see them unmanned before a laugh rings out in the ship alerting them to the presence of the Refusians . Steven decides it would be best practice for the humans to split up . Half will go to Refusis II now while the other half will search for the bomb . Maharis openly disagrees with Steven and confronts him , saying they should all leave the micro - celled humans to perish . Maharis says that he is going to Refusis II no matter what anyone says . Dassuk and some other humans join him . On Refusis II , One and his army confront Four and his army , and a full scale civil war breaks out . During this madness the launchers return . Ignoring advice to wait until things have calmed down , Maharis leaves the launcher and is immediately killed by One . The rest of the humans wait until there is a lull and form an escape . Dassuk finds the Doctor and Dodo who escape through the undergrowth and return to the launcher where they contact Steven and inform him of the position of the bomb . As they do , they encounter Four , the last Monoid standing . Steven and Venussa are at a loss as to what to do due to the sheer size and weight of the statue . The Refusian says that he will be able to help and , much to the surprise of the humans , the statue rises in the air and is placed in the loading bay . As it is ejected it explodes . When the Doctor , Dodo , the humans and the surviving Monoids return , the Refusian says he will only accept them on his planet as long as they form a peace treaty . This is agreed to . The Doctor and his companions leave , leaving the humans to wonder if he will ever return to them again . Venussa and Dassuk watch as the TARDIS dematerialises . Later as the TARDIS lands , the Doctor simply vanishes from the TARDIS control room in front of Steven and Dodo , although his voice can still be heard . Dodo wonders if this has something to do with the Refusians , but the apparently invisible Doctor says this is some form of attack . Home video and audio releases . DVD releases . A commentary for this story was recorded in October 2009 , and it was released on DVD on the following dates : Region 2 - 14 February 2011 Region 1 - 8 March 2011 Region 4 - 3 March 2011 The following special features are included : Digital releases . This story is available :