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.

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 Clara, and the Doctor stepping out, with him realizing that they are in the 22nd century. Going to the mess hall, they see that it has evidence of a fight with a knife stuck in a wall. The Doctor realizes that that took place very recently. In a corridor, they see the figures who simply examine them and leave.

In the hangar the Doctor and Clara find the spaceship and see the markings, which the TARDIS is unable to translate. The ghosts pick up axes and harpoons and attack them. They flee but the ghost follow them, albeit having to leave their weapons behind.

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.

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.
 * 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.