Under the Lake (TV story)

 was the third episode of the ninth series of Doctor Who produced by BBC Wales.

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 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 beliefs are challenged when he encounters something he cannot explain. Can it really be possible? Can ghosts 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.

O'Donnell notices Pritchard is missing and yelll 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 Lunn notice Pritchard is oddly with them, with his back turned to them. They then notice a corpse floating outside the window; Clara begins shouting man over board, but Lunn stops her as the corpse rotates to reveal it as Pritchard. Write 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!

Cast

 * The Doctor - Peter Capaldi
 * Clara - Jenna Coleman
 * Moran - Colin McFarlane
 * Cass - Sophie Stone
 * Lunn - Zaqi Ismail
 * O'Donnell - Morven Christie
 * Bennett - Arsher Ali
 * Pritchard - Steven Robertson
 * Prentis - Paul Kaye

Astronomy

 * The ghosts refer to Orion's sword.
 * The Orion Nebula, Orion, Rigel and Betelgeuse are mentioned on a map of constellations.

The Doctor

 * The Doctor uses cue cards to give apologies.
 * The Doctor once converted his radio into a clockwork squirrel.

Technology

 * The base has a Faraday cage which, when locked, the ghosts cannot enter or exit.
 * The Doctor refers to holograms.
 * The sonic sunglasses can connect to Wi-Fi.
 * A suspended animation chamber is found under the water.
 * The Drum has a submarine that can be controlled with submarine manipulator rings.
 * The Doctor refers to the fact that there were no such thing as socks, smartphones or badgers, until they came into being.
 * A submarine is contacted via Morse code.

Organisations

 * The Ministry of Defence and the British Army are mentioned, and stated to have had a facility where the spaceship found.
 * Vector Petroleum is the company in charge of the Drum.
 * UNIT is still operational.
 * The Doctor states that his UNIT security visa is 7-1-0-Apple-0-0, which is enough for him to be recognised despite it being more than a century into the future from when he is normally associated with UNIT.
 * The Drum crew refer to their colleagues above the surface as "Topside."
 * Drum Control is where the rest of the base is controlled.

Individuals

 * The Doctor states that he has met Shirley Bassey.
 * The Doctor states that Clara once had an argument with Gandhi.
 * Clara refers to people with long necks who have been celebrating New Year for two centuries.

Food and beverages

 * A cup of coffee is seen on a table; the Doctor is able to work out how long it's been there by tasting it.
 * Clara states that the Doctor raved about ghosts "like a kid who has had too much sherbet."

Languages

 * The Doctor can no longer understand British Sign Language. He believes it has been deleted from the TARDIS language bank, and replaced by semaphore. Despite this, he nonetheless correctly signs "you're beautiful" to Cass when he attempts to communicate with her and partially, and apparently unconsciously, partially signs the American Sign Language sign for "I love you" when speaking to Clara in the TARDIS about his "duty of care".

Popular culture

 * The Doctor states that he once had Peter Andre's song "Mysterious Girl" stuck in his head for two weeks, and that it drove him mad.
 * Cass refers to the Doctor doing "the Cabin in the Woods" thing.

Story notes

 * The Radio Times programme listing was accompanied by a small colour head-and-shoulders shot of Morven Christie as O'Donnell, with the accompanying caption "Doctor Who / 8.25 p.m. / Could O'Donnell and her colleagues have fallen victim to undead beings?"
 * The working title of the story (and the following episode) was Ghost in the Machine. (DWM 492)
 * This was the first episode since The Unicorn and the Wasp not to feature the sonic screwdriver.

Ratings

 * BBC One overnight: 3.74 million
 * BBC America overnight: to be added
 * UK final ratings: 5.63 million

Production errors

 * Recordings of Prichard's drowning portray his words and movement slightly differently.
 * When Clara and the Doctor run from the "ghosts" and are directed to run towards the Faraday cage (down a straight corridor), Jenna Coleman ducks below the camera.
 * O'Donnel tells the Doctor the TARDIS is on the other side of the flood doors, yet the Doctor nor Clara have told her about it.
 * In the scene in which the crew watch Prichard's death, if you pause just before the water floods into the airlock, there is a single frame of a green screen replacing the water.
 * In the second last shot in the episode, with Clara, Cass and Lunn looking outside, there is a boom microphone shadow right across Clara's face.
 * As the Doctor is explaining to the crew about ghosts, between shots, his body position and the lighting change.

Continuity

 * The Doctor uses his sonic sunglasses. (TV: The Witch's Familiar)
 * One of the ghosts was previously a Tivolian. (TV: The God Complex)
 * The Doctor has previously landed in an underwater base, in which he met with a crew that were tackling a threat that would re-animate the dead crew. (GAME: Shadows of the Vashta Nerada)
 * The Doctor uses his psychic paper as proof of ID. (TV: The End of the World et al)
 * The psychic paper tells the crew that the Doctor works for UNIT. (TV: Spearhead from Space et al)
 * One of the Doctor's apology cue cards says: "It was my fault, I should have known you didn't live in Aberdeen". The Fourth Doctor dropped Sarah Jane Smith off there rather than in South Croydon. (TV: The Hand of Fear, School Reunion)
 * Another of the cue cards says: "No one is going to be eaten / vapourised / exterminated / upgraded / possessed / mortally wounded / turned to jelly. We'll all get out of this unharmed." "Exterminated" is a reference to the Daleks, (TV: The Daleks et.al.) "upgraded" is a reference to the Cybermen, (TV: Rise of the Cybermen et.al.) and "possessed" is a reference to various races and beings. (TV: The Impossible Planet/The Satan Pit et al)
 * When the Doctor goes back on his insistence that the phantoms of the dead aren't ghosts, he notes that they aren't flesh avatars, (TV: The Rebel Flesh/The Almost People) Autons, (TV: Spearhead from Space et.al.) or "digital copies bouncing around the Nethersphere". (TV: Dark Water/Death in Heaven)
 * The Cloister Bell alerts the Doctor to a threat to the TARDIS. (TV: Logopolis, Resurrection of the Daleks et al)
 * The Doctor indirectly refers to Danny Pink (TV: Into the Dalek, et al) when suggesting Clara begin a new relationship.
 * Clara has previously stated that she doesn't believe in ghosts (TV: The Snowmen), and she and the Eleventh Doctor once investigated another "haunting" that turned out to be non-ghost in nature (TV: Hide).
 * Clara tries to "high-five" the Doctor. (TV: Hide)

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.