The Fires of Pompeii ( TV story ) The Fires of Pompeii was the second story of the fourth series of " Doctor Who " . Narratively , the story was important for explaining why the Doctor can sometimes change history and at other times cannot . Specifically , it introduced the notion of " fixed points " in time , which would later be the central theme of the television stories " The Waters of Mars " and " The Wedding of River Song " . It also continued the " Missing Planets " arc , with the Pyrovile s mentioning their home planet having been taken much like the Adipose ' s breeding planet . The episode also introduced the idea of " the destiny trap " ; the Doctor and Donna arrived in Pompeii fully aware of what was to happen . Because of this , they were unable to change events once they ' d become part of them , although they were able to save at least one person and their family . This concept would later be mentioned by the Eleventh Doctor in " The Time of the Doctor " regarding the Silence and how their efforts to kill him had created the event they tried to erase . Behind the scenes , the episode was notable for being the first major shoot outside the United Kingdom since the 1996 telemovie . Moreover , it was the first time a principal photography unit had been outside its country of production since " The Two Doctors " . The episode notably featured the first appearance of two actors within the series that went on to play bigger roles during the show ' s later seasons . It hosted a guest appearance from Karen Gillan , who would later star as the Eleventh Doctor ' s companion , Amy Pond , in series 5 , 6 and 7 . It also featured a guest appearance of Peter Capaldi , who would later portray the twelfth incarnation of the Doctor , and the fact he shared the appearance of a character in this story was not ignored . This would become an important aspect of that Doctor ' s identity when he made the connection that his face was taken from someone he previously met . Synopsis . The Tenth Doctor tries taking Donna Noble to ancient Rome for her first trip in the TARDIS , but seems to have miscalculated . Instead of seven hills , they find a single mountain billowing smoke — Vesuvius . They ' re in Pompeii , 23 August 79 AD : the day before " Volcano Day " . However , something else is horribly wrong . The Soothsayer s ' predictions seem to always be correct . . . so why can ' t they see tomorrow ' s disastrous events , the eruption of Vesuvius , the death of their city ? What is blocking their perception , and will the TARDIS team be able to walk away from a fixed point in time , saving no one from certain doom ? Well , Donna has something to say about that ! Plot . The Tenth Doctor and Donna exit the TARDIS in what the Doctor claims is 1st century Rome . Donna is amazed to have gone back in time ; everyone around them is long dead , from her perspective of being from the 21st century . Joking not to tell the locals that , the Doctor watches as Donna takes in the sights . When Donna expresses scepticism due to English words she notices on a cart , the Doctor explains that the TARDIS translation circuits are translating the local language for her ; they ' re actually currently speaking Latin . This amazes Donna further . A new idea forms in her head — what if she said something in actual Latin while her speech is being translated ? The Doctor honestly hasn ' t a clue , noting she likes to ask the hard questions . Smirking that she actually managed to stump the Doctor , Donna decides to try it out by saying " Veni , vidi , vici " to a nearby stallholder , who tells her , emphasising each syllable , that he doesn ' t speak Celtic . The Doctor explains that she sounded Welsh — " there ' s something " . Resuming their walk , Donna wonders if they stand out because of their clothing , but the Doctor explains that Rome is " like Soho , but bigger " . The Doctor explains that he ' s been here before — and " that fire had nothing to do with me . . . " Well " , a little bit ! " The two soon realise that something ' s horribly wrong . Where are those great sights — the Colosseum , the Circus Maximus , the Pantheon — that the Doctor never got to see ? Why is there one hill , and not Rome ' s famous . . . and why is it smoking ? As a tremor rocks the streets , the Doctor realises they have arrived not in Rome , but in Pompeii in August 79 — " and it ' s volcano day ! " Some time later , the Doctor and Donna meet up ; he ' s learned the date from the locals , and it ' s exactly the day " before " the eruption . The Doctor then tells her off when she tries to plan an evacuation . " Pompeii is a fixed point in history . What happens , happens . There is no stopping it . " She follows him back to the TARDIS . . . but the Doctor ' s ship is gone ! She rhetorically tells him to tell her that the TARDIS isn ' t gone ; he literally complies . " Oi . Don ' t get clever in Latin ! " Donna snaps at him . They find that the stallholder has sold it to local marble merchant , Caecilius , as a piece of " modern art " . Meanwhile , a red - hooded member of the Sibylline Sisterhood who has been following them reports to her fellow sisters and the High Priestess that the " blue box " has appeared in the marketplace . They find that this is a fulfilment of a Sibylline prophecy . However , it was to come at the time of fire , destruction and betrayal . At Caecilius ' s house , his wife Metella is preparing their prophetically - gifted but sickly daughter Evelina for the arrival of the town ' s augur , Lucius Petrus Dextrus . Their son Quintus is also present ; however , he is hungover from partying the previous night and has a bad headache . A tremor causes them to brace their valuables ; apparently , this is common . Unable to catch one , they are lucky that the Doctor arrives , and holds it in place . The family introduce themselves , and the Doctor uses his psychic paper to pass himself off as a marble inspector , which is also an excuse to get the TARDIS back . Both the Doctor and Donna assume the alias " Spartacus " . Caecilius assumes they ' re married , which they deny ; he then comes to the conclusion that they must be brother and sister as they DO look similar . The Doctor and Donna are surprised by this . Lucius arrives , and the Doctor wins a verbal joust with the augur , earning praise in return for his cleverness . The Doctor then excuses himself and Donna , and they head to the TARDIS to leave . However , he is compelled to stay when he sees Caecilius unveil a marble plaque he has produced to Lucius ' designs — it is recognisably an electrical circuit . Overhearing Lucius give prophecies , the Doctor tells Donna that they ' re in an age of " official superstition " ; prophecies are the equivalent of ten o ' clock news . Overhearing them , Evelina tells her parents that they " use words like tricksters " and are mocking them . Seeing how ill Evelina is , the Doctor is told she breathes vapours for strength , but he disagrees that it is having that effect . She then asks if that ' s his opinion as a " Doctor " . Lucius claims that Evelina ' s prophecies are easily faulted . However , when the Doctor says Lucius has been " out - soothsayed " , the augur joins Evelina in predicting the truths about Donna and the Doctor . They see their real names , naming Gallifrey and London as their true homes , Gallifrey ' s destruction , and the Doctor ' s name being " written " in the stars of the Medusa Cascade . Evelina also states that his true name is not Doctor but is " hidden " and that he is a Lord of Time . Petrus Dextrus warns the Doctor " she " is returning and tells Donna that " there is something on your back " . Evelina then faints . Later , Donna investigates Evelina ' s mysterious skin ailment . She finds that the ailment in question is that her skin is becoming petrified . Her arm has completely turned to stone . Meanwhile , the Doctor is shown a hypocaust system powered by from Vesuvius itself , from which emit monstrous sounds from " the god s of the underworld " . This system , he is told , was installed after the 62 earthquake on instructions from Lucius and the other soothsayers . From that time onwards , the soothsayers have been inhaling rock dust from these hypocausts , and all their predictions have been uncannily accurate . If so , then why have they not predicted Vesuvius ' imminent eruption ? Bribing Quintus into showing him where Lucius lives , the Doctor breaks into the augur ' s house with the boy . They find that not only is there the stone circuit that was made by Caecilius , but five others as well . Quintus is shocked by this . The Doctor explains that it ' s common practice for a criminal to acquire the required parts from different places to avoid suspicion . Meanwhile , Evelina gives Donna a , and talks about a teenager ' s life in Pompeii . Donna ' s hints about Vesuvius ' impending eruption are ignored , and she realises that " none " of the seers have foreseen it . She tells Evelina about the eruption , which the sisterhood telepathically overhear through Evelina . Their High Priestess decries it as false prophecy , determining that Donna must be sacrificed . Quintus and the Doctor , meanwhile , have been caught by Lucius . The Doctor helps him assemble the marble plaques into a circuit board . He asks who instructed Lucius to build this , saying he can help him . Dextrus takes this as offence against the gods , and threatens to have his guards kill them . The Doctor responds by trying to shake his hand — and breaks off Dextrus ' s completely petrified right arm . They then take the opportunity to flee as the Doctor knocks over the tablets . Lucius begs the gods of the underworld to go after the Doctor and Quintus as they would prevent the rise of Pompeii . A safe distance from Lucius ' home , the Doctor and Quintus hear thudding footsteps from underneath the ground . Returning to Caecilius ' s house , they find Dextrus has summoned a giant , humanoid , stone - and - magma creature , which bursts up from the hypocaust . The Doctor tells Donna to get water , while he attempts to reason with the creature . Members of the Sisterhood appear behind Donna and drag her from the room . Only Evelina sees this , but one of the sisterhood motions to her to remain silent . Unable to reason with the creature , the Doctor has Quintus throw water on it , causing it to harden and collapse into rubble . He then wonders what happened to Donna . At the altar in the sisterhood ' s temple , Donna has been tied down to a table as a sacrifice , though they cannot bind her considerable spirit . Just as Sister Spurrina lowers her knife — Donna ' s prattling voice will cease forever — the Doctor arrives , saying , " Oh , that ' ll be the day . " Spurrina is aghast , saying no man can enter the Sybil ' s temple . Entering anyway , he tells them he had met the original Sibyl after whom the order is named , and she would be " ashamed " of them . Spreading the word with the blade of a knife ? Spurrina moves to stab " him " , but the High Priestess demands to speak with the Doctor . With the curtain moved away , it is shown the High Priestess has been completely turned to stone . She confirms that it hurts , but the voices tell her it ' s necessary . The Doctor realises that somehow , the people of Pompeii are turning to stone " before " the volcano erupts . The High Priestess sees into his mind , demanding to know what a volcano is . Suspicious , the Doctor demands to know who she is . The alien , asserting control over the High Priestess , declares itself a Pyrovile ; the sisters blindly begin chanting its name . The Doctor , taking a water pistol out of his jacket , warns her that he ' s " armed " . He instructs Donna to open the hypocaust , and demands to know what the Pyroviles are doing here . The Pyrovile explains it is one several aliens who crashed to Earth millennia earlier , awakened by the 62 earthquake . Their adult form is the creature they saw at Caecilius ' villa . They are a psychic race , and have bonded with humans through the dust they breathe . The Doctor explains the psychics don ' t predict the future , but can see through time . As he questions why the soothsayers can ' t see the volcano , Spurrina informs her sisters that the weapon is harmless . The Doctor confesses she ' s right , but adds that it will sting . He fires a few squirts of water at the High Priestess , who wails in pain . Donna and the Doctor use the confusion to escape into the hypocaust , in towards Vesuvius itself . Dextrus and the possessed high priestess each declare that their Pyrovile - induced prophecy of a Pompeiian empire must advance , the latter warning that the Doctor threatens their plans . As they run , Donna tries to convince the Doctor to stop Vesuvius ' s eruption . He again refuses , telling her the eruption is a fixed point in time which cannot be stopped or avoided . Donna asks him how he knows this as " she " is basically history to him as well , but he saved her and everyone else in 2008 . The Doctor explains his Time Lord ability to see the past , present and all possible futures at once , calling it a burden . Donna presses him as to how many people died . The Doctor confirms the figure was about 20 , 000 , and she asks him if it ' s alright to let all these people die . Before he can answer , they hear a roar , hinting that the Pyrovile are aware of their presence , forcing them deeper into the volcano . Dextrus and the Cult of Vulcan take the circuit boards to the mountain . The Doctor and Donna , meanwhile , have reached the centre of the volcano . Inside it , they see what appears to be the remains of an escape pod , or something similar . Donna guesses that the aliens plan to blow up the mountain to launch themselves into space . However , the Doctor informs her they are planning something much more sinister . They are then discovered by Lucius , who summons the adult Pyrovile to hunt down Donna and the Doctor , declaring their presence a defilement to his masters ' temple . The Doctor and Donna make their way towards the pod , briefly fending off an adult Pyrovile with the water - pistol . Reaching the pod , the Doctor politely asks Lucius as to the Pyroviles ' plan before they die . Lucius announces that his masters ' plan is to expanding beyond Pompeii , to conquer the whole world . Donna points out that the Pyroviles could just go home , but Lucius retorts that their home planet , Pyrovillia , was " taken " . Thus they will stay and conquer Earth , boiling its oceans and burning it to cinders . The Doctor and Donna lock themselves in the Pyrovillian ship . The Doctor finds the Pyrovile are using Vesuvius to set up a fusion matrix to convert millions of humans into Pyroviles . The matrix will bleed off so much of Vesuvius ' pent - up energy there won ' t be enough to trigger the eruption — " this " is why the soothsayers have been unable to see it . There won ' t " be " an eruption anymore ! The Doctor can switch off the Pyrovillian circuitry and save the world from conquest , but he will cause the eruption and the deaths of himself , Donna and twenty thousand people . And if Pompeii is destroyed , it ' s not just history . . . " it ' s me " . They choose the latter as the lesser of two evils , and , together , reverse the machine . Vesuvius roars into life , and both Lucius and the Pyrovile s , at the centre of the explosion , are destroyed almost instantly . The explosion bursts through the top of the mountain as Vesuvius unleashes her fury . The residents of Pompeii watch in terror as ash falls upon them , thinking the sky is falling . Meanwhile , the Pyrovillian escape pod holding the Doctor and Donna is launched into the sky and lands between Vesuvius and Pompeii . The two run for the safety of the TARDIS . As they do , Donna tries to inform the citizens where it ' s safest to flee , but they ignore her in panic . They reach the Caecilius family ' s home , where the Doctor ignores their pleas for help as Donna yells at him . With the TARDIS engines starting up , Donna is forced to board as well . As they dematerialise , Donna urges him to return and save the citizens . The Doctor refuses , saying if he could go back , he would — just as he would go back and prevent the destruction of Gallifrey , which also burned . Donna tearfully pleads with him — if not the city , then just save someone . Just one person ! The Doctor relents , and rematerialises the TARDIS inside the Caecilius home , where the family are huddled in a corner awaiting death . He offers them his hand , and takes them into the safety of the TARDIS . The Doctor , Donna , and the Caecilius family gloomily watch from the hills as the pyroclastic flows from Vesuvius destroy Pompeii . The Doctor explains why Evelina ' s visions have stopped — the massive explosion of Vesuvius caused a tiny rift in time that lead to the future where the Pyroviles won ; however , now that future has been prevented , she can longer see the future . He promises that Pompeii will be remembered . They then wonder who the Doctor is and why his " temple " has such size within . Caecilius , awed by the fury of Vesuvius , coins the word " volcano " , but grieves for the people who are getting killed by the eruption . The Doctor and Donna leave , with him acknowledging that she was right — " Sometimes I need someone " . Six months later — in early 80 — the Caecilius family has resettled in Rome . Lobus Caecilius has re - established his marble business , now worrying about a deal with the Egyptian s that may set up his family for life . Evelina is a healthy and happy teenager once again , and is dating and wearing trendy outfits , much to her father ' s consternation . Quintus has been the most affected of the family — he is now training to be a doctor . He is told to give thanks to the household gods before he leaves for his studies . Doing so , Quintus smiles at the image of the gods and thanks them ; the marble bas - relief shows the family ' s household gods to be the Doctor and Donna , and their temple the TARDIS .