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 brought up that Clara was starting to lose touch with her humanity and become more and more like the Doctor. The Doctor catches this and tries to get her to see, but it turns out to have been in vain.

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. However, another member of the crew, Bennett, firmly states that the ship is not Earth technology. Annoyed, Moran suggests that it was an experimental craft left behind by the government when the town flooded.

They get the ship open, Lunn is told to get a torch. Lunn does so, but glimpses a ghostly figure reflected in the glass. He reluctantly hands Moran the torch. The rest of the crew enters the ship, finding it sparse except for an elevated platform and a flower-like pattern on the back wall. Moran notices four strange markings engraved on the wall, directing everyone's attention to it. In the meantime, Cass is telling Lunn that he cannot go inside the ship. Moran, along with Bennett and another crew member, O'Donnell exit the ship to find out why they're arguing.

Inside the ship, Pritchard examines the pattern on the wall, only to be spooked by the reflection of the ghost. He dodges being touched by the ghost, who activates the engines of the ship. Moran pushes Cass out of the range of the boosters, taking her place in being burned to death. The base announces it has detected a fire and will activate the fire suppression system; the sprinklers go off as everyone rushes or is rushed out of the room before it is sealed off.

O'Donnell bangs on the sealed door, demanding they go back for Moran, but is told it is impossible by the rest of the crew; there is no way he could have survived that. 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; he appears to be saying something. He is joined by the same ghost, and the two reach out towards the crew... 3 days later, the facility is a wreck, being seemingly empty. The TARDIS appears, with the Doctor exiting; he notes that the TARDIS is upset and asks why she's unhappy, examining his ship. Clara pops her head out, asking if they could go back to the planet where people with long necks have been celebrating New Years for two centuries, as she forgot her sunglasses. However, the Doctor isn't listening. She exits, asking where they ended up; he says that they've ended up in an underwater base in the 22nd century. They explore, with Clara asking if they can go on another adventure, even accusing the Doctor of "itching" to save a planet, or solve a mystery. He smiles behind her back.

They enter the mess hall, finding it in shambles; "wish granted" the Doctor tells Clara. There are clear signs of a struggle, such as a knife in the wall. There are also signs that someone might still be alive, as provisions were taken in a hurry. The Doctor sticks his finger in a cup of coffee, explaining whatever happened occurred less than 1/3 of a day (8 hours) ago.

The Doctor and Clara continue exploring, finding the two ghosts kneeling in the hall. The Doctor calls out to them, and they turn around. The ghosts approach, examining them and then walk off. This leads the Doctor and Clara to the hanger, where he confirms the ship is of alien origin. They go inside, with the Doctor drawing Clara's attention to the strange markings; he notes that something is VERY wrong as the TARDIS isn't translating the symbols. Clara notices the ghosts have returned, and the Doctor asks them if they wanted them to see the symbols. The ghosts begin arming themselves. The Doctor wonders if it was something Clara said, as she once got into a fight with Gandhi. Moran fires a harpoon, which misses them. The Doctor and Clara flee. The ghosts phase through the wall, leaving their weapons behind. As the duo run through the halls, the find O'Donnell in a doorway, signaling for them to come in. They comply and run into the room, with the door shutting behind them; the room is filled with cots and supplies. For some reason, the ghosts give up and walk away. Pritchard demands to know who they, prompting the Doctor to brandish the psychic paper and introduce himself and Clara. To Pritchard's shock, it says they're from UNIT; the Doctor is surprised, given he DOES work for UNIT. O'Donnell shakes the Doctor's hand, glad to meet him; she calms down, saying he does a good job. The Doctor asks who's in charge, as he needs to know who to ignore. Lunn explains Cass is, but Pritchard claims leadership as he represents Vector Petroleum.

The Doctor asks about the things trying to kill them, to which Lunn begins translating for Cass. However, the Doctor claims to know sign language; Cass starts explaining. Unfortunately, the Doctor admits that he cannot understand her, as he might have deleted sign language for semaphore in the TARDIS data banks. Cass explains that this trouble started when they brought the ship on board; their commanding officer died, then the ghosts showed up and started trying to kill them. For some reason, they are unable to enter this room, which is a Faraday cage. However, the Doctor doesn't believe in ghosts, noting one of them is a Tivolian; normally, said alien would be a submissive coward, not an aggressive killer. Bennett laughs in joy, because he was right about the ship. The base announces that day mode has begun, prompting O'Donnell to sigh in relief. Everyone begins exiting the room, prompting the Doctor to worry about the ghosts; she tells him that they only come out at night. "Weird how that's not comforting." Clara quips.

As they go back into the hanger, the Doctor wonders why the crew didn't abandon base with murderous ghosts around. Pritchard explains that it was his idea as there is equipment down there worth millions. The Doctor coldly tells him "I understand; you're an idiot." He questions as to why the base as a faraday cage, to which he learns is because the mining equipment runs on nuclear fission; the Doctor notes they are being attacked by ghosts in an underwater nuclear reactor, sarcastically asking if anyone has a peanut allergy he needs to worry about.

They go back into the ship, where the Doctor asks what happened to the things they've removed. However, the crew have no idea what he's talking about. The Doctor shows them that a stasis chamber for the pilot is missing; it's typically used for long flights. Another thing missing is a power cell, which has enough power to zap a ship from side of the galaxy to another. Cass and Lunn argue, which Lunn explains is due to her saying it's not safe for him to go inside; he argues that it's not safe anywhere. The Doctor goes over what's happening; they are being attacked by two creatures that have taken the form of Moran and a cowardly alien, they are kind of see through, can move through walls, and they only come out a night. Catching onto the Doctor's train of thought, Clara begins to question what he's about to say. The Doctor smiles. Back in the base's control room, the Doctor giddily shouts that they ARE dealing with ghosts. However, Clara points out he "poo-pooed" the ghost theory. The Doctor goes on to say many things didn't exist, and then they did. He goes on to explain that the ghsots aren't flesh avatars or, digital copies from the Nethersphere; these people are actually, truly dead! The Doctor is met with silence. Bennett reminds the Doctor that Moran was their friend. Clara whispers that he needs "the cards". Seeing she's right, the Doctor turns around and begins sorting through cards. However, an annoyed Clara takes them from him and sorts through them, finding the right thing. She hands it to the Doctor, who reads off that he will do all he can to solve what caused the death of their loved one. The Doctor then immediately goes back into his maniac happiness, asking why the crew isn't more excited. They now have proof that you can come back after you die; "sure, you come back a bit murdery" he admits. He thinks of all the things he would ask a ghost about their state of existence.

Suddenly, the base states that it's going back into night mode. O'Donnell calls over the speakers to warn everyone, especially Pritchard, who was not with them. It turns out that Pritchard had gone out to search for the power cell, but found nothing. He thinks he sees Bennett outside the chamber, taking off his helmet; Pritchard thinks he can claim the ship and its contents as assets. However, much to his horror, he finds the ghosts outside. Moran sees the controls and activates them, letting water in as Pritchard rushes to get his helmet back on.

In the mess hall, Lunn and Clara have gathered supplies and find Pritchard standing in the room with them. However, Lunn notices a body floating outside; he yells man over board, but Clara tells him it's Pritchard's corpse. The one with them is a new ghost. The ghost grabs the legs of a chair and advances on them, ready to kill; however, right before it can do anything, O'Donnell manages to switch the base back into day mode, allowing everyone some peace. In the control room, they watch footage of Pritchard being killed. The Doctor notes the ghosts are getting smarter, figuring out how to use the base against the crew; they know they can only exist at night mode, so they've been reprogramming the base. However, Cass has had enough with losing her crew, telling the Doctor to stay at his own peril, but she is getting her friends out of this haunted house. O'Donnell contacts Topside, who inform them a sub with a full medical crew is two minutes away; they were contacted by Morse code that two of the crew were critically ill. The Doctor takes the phone, stating his UNIT security visa and telling Topside that an unidentified contagion is on the base; the base is to be quarantined and the sub recalled.

Bennett wonders why he did that, to which the Doctor explains; none of them sent the message, so the ghosts did. They want those extra people down here, and "I'm pretty sure it's not so they can form a boy band." The Doctor then compliments O'Donnell on her brilliance, telling her to put the base back into night mode; not knowing why the ghosts are trying to kill them is what's getting them killed. It's time they took control of the situation.

However, the Doctor's attention is caught by the Cloister Bell ringing from the TARDIS. He and Clara run back, with the Doctor explaining the ghosts are a paradox; the TARDIS cannot stand to be around "wrong" things. The Doctor puts the brake on, to keep the TARDIS from leaving. Clara decides to head back out, but the Doctor tells her not to "go native", explaining that there is only room for one version of him in the TARDIS. Clara tells him that she understands.

Night more is reactivated. The plan is simple, using Bennett, Clara and Lunn, (as the Doctor needs to coordinate them, and O'Donnell is needed to control the base) they will set up a kind of relay race to lure the ghosts into the Faraday cage; once inside, the ghosts will be unable to escape. Bennett finds the ghosts in the mess hall, getting their attention; he rounds a corner and hides behind a door O'Donnell lowers. Clara is up next, she gets their attention and follows suit; however, when it's time for Lunn to get followed, only Pritchard's ghost follows him. Lunn is able to round a corner, but is seen by the ghost; it phases through the door and approaches him. As there is no camera in that room, the Doctor yells for Lunn to tell him what is happening. The ghost leans near Lunn, but as soon as it sense something about him, turns around and leaves. A relieved Lunn tells the Doctor that it left him alone; however, this only adds onto the confusion, as the ghosts have been trying to kill everyone else there.

Pritchard's ghost rejoins the others chasing Clara, who manages to give them the slip. The Doctor informs Bennett, who is around the corner from the ghosts, that he's next. Bennett gets there attention and runs towards the Faraday cage, telling the Doctor to cue Clara. Clara walks into view of the open door as Bennett rounds a corner. The ghosts advance on Clara, who is revealed to be nothing more than a hologram. The door is shut by the Doctor, who tells the ghosts that they need to chat; unfortunately, they're a bit too murdery, so they need a time out.

Connecting his sonic sunglasses to the base's Wi-Fi, the Doctor asks Cass to tell him what the ghosts are saying. However, the glass on the window is too thick and the ghosts are too far away. The Doctor enters the room, and Moran's ghost thrusts its hand into his chest. Seemingly in shock, the Doctor says "Cold..." before smirking at him; the ghosts cannot physically harm them, so that's why they've been using tools. The Doctor asks Cass for what the ghosts are saying, learning they are saying "The dark, the sword, the forsaken, the temple" over and over.

The Doctor returns to the control room, explaining the ghosts are not a natural phenomenon; someone has denied these people their deaths, using their souls as transmitters that are broadcasting out into space. The more they kill/recruit, the strong the signal gets, hence why the called down the med sub. The Doctor explains that the "dark" is space, the "sword" is Orion's Sword with the Earth as the tip, the "forsaken" is the flooded town, and the "temple" is an abandoned church in the town. However, he then adds a new piece of information; when they heard those words for the first time, they weren't surprised by it. The Doctor goes on to explain that the words were already in their heads, as the words on the ship rewrote the synapses in their brains. "It's a song you can't stop singing, even after you're dead." The Doctor tells the crew that they are welcomed to leave and go back to safety, but then tells them that they could instead stay and be part of history. Cass decides to stay, with Lunn also saying he'll stay. O'Donnell doesn't care if her life is in danger. A rather annoyed Bennett tells the crew that if he does die, they know he WILL come back to haunt them. The Doctor and Clara smile.

The Doctor grabs a map and manages to pinpoint where the church is in the town. Controlling a scavenging robot, Bennett directs it to the church, with the camera feed also showing up on the control room monitor. In the basement, the robot finds a large rectangular box that shows little signs of erosion. The Doctor explains that they are looking at the missing stasis pod from the space ship; he tells Bennett to bring it aboard. The stasis pod is brought inside the base, with the Doctor eager to examine it. However, much to his annoyance, he finds that it has a deadlock seal; there is also a timer on the device, which shows when it will open. The occupant is the one responsible for the ghosts, but what it's intentions are beyond that are a mystery; is it simply causing the deaths of others to save itself, or is it actually calling the rest of its race to attack earth?

Suddenly, the base begins flooding; O'Donnell explains that changing the day settings so much has caused the computer to malfunction; it thinks the reactor has gone critical and needs to be flooded. The Doctor, O'Donnell and Bennett manage to get to the TARDIS, but the corridor to it is sealed off before Clara, Cass and Lunn can get there. The Doctor promises to come back for her. He goes back to the TARDIS, where he decides it's time to go find out how this all started. In the mess hall, Clara is slightly worried, but tells Lunn and Cass that the Doctor will come back for them; there is no need to panic. However, Lunn notices a ghost out in the town; it means someone else must have died, since the ghosts cannot get out of the faraday cage. Clara looks out to examine the ghost, and become completely horrified. This new ghost is 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, along with 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.
 * In the mess hall, there is a painting on the wall of a sea serpent attacking sailors, which bears facial similarities to the Fisher King.
 * Cass appears to have good reasoning skills, as she doesn't let Lunn into ship; it's likely she knows that seeing the symbols is somehow connected to the ghosts attacking them.

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.

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.