Under the Lake ( TV story ) It saw the series revisit the concept of ghosts and hauntings , last explored in the television story " Hide " . The episode poses another explanation for the apparitions , in this case as resurrected transmitters of an alien presence ' s signal . It also continued the thematic concept of the Doctor apparently facing death , with the end of the episode setting up yet another opportunity for the Doctor to reflect on his mortality . Synopsis . Arriving on an underwater base under attack , it ' s up to the Twelfth Doctor and Clara to save the frightened crew . But also onboard is an alien spaceship , and the base is being haunted by the most impossible of things . The Doctor ' s deepest belief s are challenged when he encounters something he cannot explain . Can it really be possible ? Can ghost s be real ? Plot . In an underwater mining facility based in Scotland , 2119 designated the Drum , the captain , Moran , is recording a log in his journal . Moran states that the team has discovered a small craft located on the bank , and , as they are unable to analyse it from within the base , they have brought it inside , where he and the crew will investigate . A crew member named Lunn interprets the sign language of another crew member , Cass , saying that the reason for its sudden appearance is due to underwater movement and shifts on the floor of the lake . Another crew member named Pritchard recommends they discuss ownership the spaceship , prompting Moran to tell everybody to stop calling it a spaceship , as they don ' t know what it is . Bennett , another of the crew , is adamant that it ' s not technology that could have existed back in the 1980s . The crew enter , and Moran notices something inside the craft , asking Lunn to hand him a torch . Lunn does so , but glimpses a ghostly figure reflected in the glass . He reluctantly hands Moran the torch . Moran investigates four strange markings on the wall , whilst Lunn asks Cass why he shouldn ' t go inside . Whilst they bicker , Pritchard cries out as he glimpses the ghost , accidentally starting the engines . Moran pushes Cass out of the way of the boosters ' range , but is struck by the blast , forcing the crew to retreat , leaving him behind . O ' Donnell , another crew member , bangs on the sealed door , demanding they go back for Moran , but is told it is impossible by the rest of the crew . She yells at Pritchard for messing with the controls , but is interrupted as Cass screams . She turns , startled to see a ghostly Moran , with gaping back holes for eyes hovering in front of her . The same figure , named Albar Prentis appears , and the pair reach out to the crew . . . 3 days later , the facility is a wreck , being seemingly empty . The TARDIS appears , with the Doctor stepping out , realising that they are in the 22nd century . The Doctor notes that the TARDIS is in a foul mood , as if something near by is upsetting her . Laughing , Clara pops her head out of the TARDIS , asking if they can go back to the planet where people with long necks have been celebrating New Years for two centuries ; she left her sunglasses and most of her dignity there . Still amused , Clara accuses the Doctor of " itching " to save a planet . He smiles back , deciding to check out the area . They investigate , the mess hall , which has evidence of a really bad fight with utensils and furniture throw about . Finding a knife lodged in a wall , the Doctor tells Clara that she got her wish for a mystery . She wonders how long the place has been empty , since many supplies are missing from the mess hall stock . The Doctor stick his finger in a mug of coffee , explaining that the fight happened right hours ago . They resume searching for a crew , finding the two ghosts kneeling in the corridors . The Doctor calls out to them and the two ghosts approach , startling the duo . Clara is calmed by the Doctor , who thinks that the ghosts are only curious about them ; the ghosts walk down the corridor and through a wall . The Doctor and Clara follow , finding themselves in the hanger ; Clara wonders about the strange vessel the crew found , thinking it could be a government project from this era . However , the Doctor confirms that it ' s alien in nature . They go inside , finding it undisturbed since the crew first investigated ; they find the strange writing on the wall . The Doctor is shocked by this , as it isn ' t being translated by the TARDIS translation circuit . However , before he can ponders this further , Clara draws his attention to the outside of the ship , where the ghosts have reappeared . The Doctor greets them warmly , wondering if they wanted them to see this strange writing . The ghosts do not respond , only walking over to a wall to grab weapons . Clara notes that this is not going well . The Doctor wonders if Clara said anything to offend them , as she once even got in a fight with Gandhi . Moran fires a harpoon gun at them , but misses . The Doctor and Clara run out of the hanger ; the ghost follow through the walls , but are forced to leave their armaments behind as they are not intangible like them . Now back in the corridors , they run away from the ghosts . At the end of the corridor , O ' Donnell opens a door , yelling for them to enter . They comply and the door is slammed behind them . The room is filled with living supplies and the remaining six members of the crew . A smug man by the name of Pritchard tells them that if they don ' t work for Vector Petroleum , they are in big trouble . The Doctor brandishes the psychic paper and introduces himself and Clara . Shocked by what he sees on the psychic paper , Pritchard yelps that they ' re from UNIT ; " Well , if that ' s what it says . " the Doctor passively says . O ' Donnell shakes his hand , happy to meet a Doctor . The Doctor asks what the ghosts are , dismissing the idea they are ghosts ; he asks to know who ' s in charge , so he can ignore them . Lunn explains Cass is , but Pritchard claims to be as he ' s from management . The Doctor ignores Pritchard , asking what happened ; Lunn begins translating for Cass , but the Doctor tells him that he can understand sign language . Cass begins explaining , but the Doctor asks her to stop ; he thinks he deleted sign language from the TARDIS for Semaphore . Lunn resumes translating ; the mole alien killed Moran as soon as the ship got brought on board and the ghosts have pretty much been trying to kill them since . The crew hide out here in the Faraday cage as the ghosts cannot enter it for some reason . The Doctor notes how odd it is for the alien ghost to be aggressive as Tivolians are so cowardly , " They wouldn ' t even say boo to a goose . " A recorded voice announces that day mode is on . Everyone starts leaving the room , confusing the Doctor ; O ' Donnell explains that the ghosts only come out at night . Everyone returns to the hanger , with the Doctor curious as to why they haven ' t abandoned base . Pritchard takes credit for that , explaining Vector Petroleum would lose tons of money if they abandoned the base . The Doctor calls Pritchard an idiot for not valuing human life over money ; he recaps the entire ridiculous situation , sarcastically asking if anyone has a peanut allergy . The Doctor goes back into the ship , asking where the missing parts are ; this confuses the crew as they haven ' t touched the ship since they brought it on board . The Doctor explains that a power cell is missing and so is the suspended animation chamber for the pilot . He begins to ramble on what he ' s observed about the ghosts , grinning more and more as he comes to a conclusion . Clara , having caught on to his train of thought , wonders if he ' s actually thinking . . . " " They ' re ghosts ! " " the Doctor exclaims back in the control room . Clara points out that he completely shot down the idea of ghosts . However , the Doctor counters Clara , telling her that there was no such things as socks , smartphones or badgers until they suddenly did exist . He further explains these things are not Autons , Flesh avatars or Nethersphere copies ; these people are actually , truly dead beings . Met with silence , the Doctor wonders why everyone is staring at him ; they explain Moran was their friend . Clara tells him to bring out his cards . Realising Clara is right , the Doctor pulls out a stack of cards with kind and apologetic things written on them . Annoyed the Doctor is taking too long , Clara takes the right one out and the Doctor reads it off , promising to solve Moran ' s murder . With that done , the Doctor resumes being excited at the idea of wrestling down a ghost and asking it questions about what it ' s state of existence is like . He does note he subconsciously noticed the ghost can only handle metal objects . Suddenly , the base announces that it ' s going back into night mode . As the others prepare to return to the Faraday cage , O ' Donnell notices Pritchard is missing and yells over the speakers for him to get to safety . However , Pritchard was out searching for the missing power cell ; greedy , he wanted to find it to gain favour with his employers , along with the rest of the alien tech . Taking off his diving helmet in the decompression chamber , Pritchard notices a figure outside and assumes it ' s Bennett . However , to his horror , it ' s Moran and the Tivolian . Before Pritchard has a chance to put his helmet back on , Moran opens the gate and water starts rushing in . In the galley , Clara and Bennett , while gathering supplies , notice Pritchard is in the room with them , with his back turned to them . They then notice a corpse floating outside the window ; Bennett begins shouting there was a man overboard , but Clara stops him as the corpse rotates to reveal it as Pritchard . Right as Pritchard picks up a chair to attack them with , the base suddenly goes back into day mode ; O ' Donnell managed to fix the problem and restore the system to normal . Back in the control room , everyone watches footage of Pritchard ' s death . The Doctor notes the ghosts got smarter ; they ' ve figured out how to use the base to kill , since the Faraday cage keeps them out . Since they can only come out at night , they reprogrammed the base ' s timer to trick everyone into a false sense of security . The Cloister Bell begins ringing from the TARDIS . The Doctor and Clara race back inside , where the lights in the control room are flashing red in rhythm of the ringing of the bell . Clara is confused ; the Doctor explains " you live and you die ; those ghosts are a contradiction . " This is why the TARDIS was upset when they got here ; she wants to get away from the ghosts . Clara asks him what they should do . The Doctor calmly turns a crank , shutting off the ringing ; he just putting the parking break on to keep the TARDIS still . Clare discards her jacket , ready to head back out . However , the Doctor stops her , explaining that despite the infinite space there is inside the TARDIS , she shouldn ' t " go native " and start acting like him . Clara thanks him for the words . They return to the control room , where the Doctor is eager is go ghost hunting . However , Cass now has command without Pritchard in the way ; she orders the base abandoned , so they can send down someone to take care of the ghosts . She then adds that the Doctor can stay and do his investigation at his own peril . O ' Donnell contacts Topside , only to learn a Morse code SOS was sent for a full medical team . The Doctor takes the phone and states his UNIT security visa ; he tells Topside the Drum will be under quarantine . When asked why he did that , the Doctor tells everyone that the ghosts made that call and " " I ' m pretty sure it ' s not so they can make a boy band . " " The ghosts want people here to kill , but the reason why is still unknown . Remembering the brilliance O ' Donnell showed in returning the base to day mode , the Doctor tells her to change it back ; they need to capture the ghosts and question them about their motives . He offers everyone the chance to leave , as it will be less of a burden to him ; however , he adds that this could be a rare chance to understand something out of the norm . Everyone agrees to help ; though Bennett sarcastically adds that they now he will come back to haunt them if he dies . The plan is simple , use Lunn , Bennett and Clara as bait to lure the ghosts to the Faraday cage ; the Doctor , Cass and O ' Donnell will monitor things from the control room ( being deaf , Cass cannot help with being bait as she cannot be prompted over the radio ) . Bennett finds the ghosts in the galley , yelling for their attention ; they give chase as the Doctor tells him where to go over the radio . As soon as Bennett turns a corner opposite of Lunn , Lunn runs out and becomes the ghost ' s target . However , when it comes time to pass the ghosts off to Clara , only Moran and the Tivolian follow her ; Pritchard is still following Lunn . The Doctor attempts to get Lunn away to an area he can seal off , but Pritchard catches sight of him just as the door seals . The ghosts enters much to Lun ' s horror ; he cowers in a corner as the ghost leans in . However , it senses something off and leaves . Lunn tells the Doctor the oddity over the radio . Pritchard rejoins the other ghosts chasing Clara , as she passes them of to Bennett . Bennett makes it to the Faraday cage , where Clara is inside ; however , when the ghosts go to attack , they pass right through her . It ' s a hologram of Clara , not the real thing . The cage is sealed behind the ghosts by the Doctor , who tells them they need to talk . He sends what he ' s seeing through the sonic sunglasses back to the monitor in the control room ; however , Cass cannot read the lips of the ghosts because of the glare of the window . Despite the protests of everyone , the Doctor enters the cage to give Cass a better look at the ghosts . Moran sticks his hand through the Doctor , who says it ' s cold before jovially asking if the ghost agrees . Without access to the controls or anything metal , the ghosts are no longer a threat . Cass now has a good view of the ghosts and finds they are repeating the same four words : the dark , the sword , the forsaken , the temple . The Doctor is confused for a moment , but then has an epiphany . Back in the control room , the Doctor explains that these words are coordinates that are leading to the flooded town outside the base . The meaning of the message is something he hasn ' t figured out ; is it a call for help or an invasion signal . The Doctor then asks everyone if something is still bothering them ; after a moment , Cass says it ' s the temple part of the message . The Doctor uses a map to reveal this message is pointing to an old church , where something commanding the ghosts is in waiting . Bennett uses a remote - controlled exploration device to go through the flooded town to find the church . Inside the basement of the church lies the missing suspended stasis chamber . The chamber is brought on - board , with everyone curious . To the annoyance of the Doctor , the chamber has a deadlock seal , which means he can ' t open it with the sonic ; whoever is inside is snoozing away , waiting to be rescued . With no answers , the Doctor decides to think back to when he first arrived to come to a conclusion . When he and Clara first arrived , the ghosts made no attempt to kill them ; instead , they lead them to the ship , and THEN attempted to kill them . It ' s at that moment , the Doctor has a realisation . He runs back into the ship and scans the symbols with the Sonic sunglasses , muttering about how the TARDIS can ' t translate the writing . The Doctor walks out of the ship , asking Cass ( the next smartest person in the room ) if she feels something is still off . She tells him the writing in the ship ; he explains they act like magnets , creating a localised magnetic field . The Doctor then asks Clara why he doesn ' t have a radio in the TARDIS ; she explains he turned into a clockwork squirrel . The Doctor says it ' s because he once got " Mysterious Girl " stuck in his head for two weeks ; " " I was begging for the brush of death ' s merciful hand . " " The Doctor calls the words an ear - worm , that quite literally rewrites the synapses in a person ' s brain . They were not surprised by the message , as it was already in their heads ; it ' s also how the ghosts are getting created . They are not a natural occurrence . Suddenly , the base starts acting up . O ' Donnell explains that messing with the day mode of the base so much has caused the system to malfunction and assume the reactor is in danger of going critical . It ' s being flooded , which means unless they get to the TARDIS , they are stuck here with the ghosts . The Doctor , Bennett and O ' Donnell are the only ones who make it to the other side of the base before the doors seal . He promises to come back for Clara . Back in the TARDIS , the Doctor says that he needs to go back before the flood to find out how all this started . Bennet and O ' Donnell are stunned at being inside the TARDIS . The TARDIS vanishes into the 1980s . In the galley , Clara tells Lunn that they need to wait for the Doctor . He always comes through , she usually has to put up with listening to how he did it . Lunn freaks out at something outside the window ; its a ghost ! However , all three are still in the cage . Clara takes a good look at it , instantly becoming horrified ; it ' s the ghost of the Doctor ! Home video releases . DVD releases . " Under the Lake " was released on DVD as part of " Doctor Who : Series 9 , Part 1 " on November 2 in region 2 and November 3 in region 1 . Blu - ray releases . " Under the Lake " was released on Blu - ray as part of " Doctor Who : Series 9 , Part 1 " on November 2 in region 2 and November 3 in region 1 . External links . Transcript of " Under the Lake " at Chrissie ' s Transcripts Site