Thin Ice (TV story)

 was the third episode of series 10 of Doctor Who. It was written by Sarah Dollard, directed by Bill Anderson and featured Peter Capaldi as the Twelfth Doctor and Pearl Mackie as Bill Potts.

The events of this story follow on directly from Smile, with the TARDIS arriving in London just moments after the Doctor and Bill left the planet Gliese 581d.

Bill repeats many of the concerns that Martha Jones expressed in TV: The Shakespeare Code word for word, such as the fact that she has arrived in a time period when black people were still enslaved and treated poorly. Unlike Martha in that episode, Bill experiences racism from Lord Sutcliffe. Bill also initially thinks that time travel worked like the movie The Butterfly Effect, where she could erase herself from existence by the smallest change to history.

The Doctor did not run into his previous incarnation, who had brought their wife River Song to the last Frost Fair to hear Stevie Wonder sing for her birthday, as was revealed in A Good Man Goes to War.

It is also the first episode since 2006's New Earth that a character has almost said a strong swear word, only for the scene to change.

The Doctor's morality and ability to be indifferent towards people dying is also brought up again. As the Doctor goes on to explain, he has to put his outrage aside and keep a cool head to prevent even more losses. He is also shown not to tolerate racism, as he punches out Lord Sutcliffe for insulting Bill.

As was the case in Cold Blood and Kill the Moon, the Doctor shows a refusal to do anything that could drastically alter the history of Earth on his own. Instead, he makes his companion make the decision.

Synopsis
Trying to get back to the university before Nardole notices he broke his oath, the Doctor accidentally lands himself and Bill in the past, at the final frost fair in 1814. He decides to enjoy the unexpected trip.

However, something sinister is lurking below the frozen Thames.

Plot
The Doctor and Bill are shocked to find themselves on the ice of one of the Frost Fairs. Heading back inside, the Doctor moves the TARDIS onto a bridge, just in case it falls into the ice.

Bill thinks they've gone to a parallel universe; however, the Doctor tells her that they travelled in time, this is London, just in the past. The Doctor is up to going to the fair, but Bill points out that they're in an era where her race was enslaved. He dismisses her worries, telling her where to find the wardrobe. Bill then laughs that the TARDIS has dresses.

Elsewhere, a drunken man follows the lights across the ice to an area of thin ice before being sucked under leaving only his drink bottle behind. Bill steps outside the TARDIS later, dressed in period clothing. The Doctor exits next, wearing a suit and top hat. Bill wonders if there's anything they need to be on the lookout for, as the Doctor shuts the door. As they leave the TARDIS, they miss an alert message that a large creature is living in the River Thames.

As they walk, Bill asks about being in the past; she wonders if the future could be changed by the slightest things she does. The Doctor jokes their friend stepped on a butterfly and ceased to exist; now Bill can't even remember him. Bill notes the Doctor's joking; they were the only passengers in the TARDIS. As they walk, a street urchin offers them a flyer for the Frost Fair on the Thames, which they attend.

Bill notes that Regency London is a lot more racially diverse than she remembers from the movies. The Doctor remarks that "history is a whitewash", even suggesting that Jesus Christ could have another race other than Caucasian. Whilst enjoying the festivities, Bill notices strange green lights under the ice and follows them; the Doctor reveals he had noticed them too, but let Bill have fun while she could before they get to work. The Doctor accidentally insults a pie man, who he knows cheats at a coin toss. The Doctor and Bill are approached by a girl looking for her dog that has gone missing, the girl wanting their help. However, the Doctor deduces that she is trying to con them (he congratulates her), catching a boy's arm as he attempts to pickpocket his sonic screwdriver from behind, only for the girl to kick his leg, enabling the pair to flee.

Inside their hideout, the boy, Spider, wonders what the sonic screwdriver is. Kitty doesn't know, but guesses it could be worth a lot of money. They are surprised by the Doctor and Bill, who give chase. However, Spider becomes distracted by the green lights, despite Kitty yelling at him for not sticking close to her. Spider is sucked under leaving only his outstretched arm, with the sonic screwdriver, protruding through the ice.

Though the Doctor tries, he cannot save him and only manages to retrieve his screwdriver. His relief at having done so and his seeming lack of care towards the boy's death causes Bill to run off and then confront him. She demands to know how many people he's seen die- he doesn't know- and how many people he's killed- he doesn't say. The Doctor tells her that he is 2000 years old and doesn't have the time for the luxury of outrage otherwise more people would die.

The girl, Kitty, takes the Doctor and Bill to meet the rest of the urchin gang- including the girl who handed Bill the flyer. After gaining their trust by giving the children the food the Doctor stole and reading to them, the urchins explain that a man with a tattoo of a ship on his hand pays them to lure people onto the ice by handing out flyers.

Bill and the Doctor put on dive suits and walk out onto the ice. They cannot hear each other with the helmets on and the lights begin to surround Bill. She throws her lantern at the Doctor to gain his attention before she is sucked under the ice. The Doctor jumps through before it reseals and discovers a giant sea creature chained at the bottom of the river. Bill sees the hat belonging to the boy who was sucked under in its mouth before they come back to the surface. Back on the surface, Bill notes that the creature sounded miserable from its imprisonment. Finding the pie man harvesting the angler fish, the Doctor yells for him to stop. They stop him, learning he fishes out the angler fish that lure in food for the monstrous fish below the ice. Bill is sickened to learn the pie she ate was made out of those fish. The Doctor asks if the man's seen someone with a tattoo of a ship. As he can't get an answer, the Doctor instead asks if there's anything else strange.

Told about dredgers extracting muck out of the Thames, the Doctor and Bill go to investigate. Bill is less than impressed at the sight of mud, wondering why there as the creature as at the other end of the Thames. The Doctor tells her that the head is at the end; they're at the other end now.

Using the psychic paper under the pretence of conducting an inspection on the orders of a Lord Sutcliffe, the Doctor gets the foreman to tell him about the mucking by complementing his intelligence. The foreman tells them that the waste of the creature is more efficient than coal and can even burn underwater making it a highly valuable resource. The Doctor realises that it could be used as space fuel. When asked if he'll still have to work as a foreman, the Doctor half-jokes that he can assure him that he won't be having that job much longer. They visit the manor home of the employer Lord Sutcliffe to determine whether he is an alien. The Doctor insists he does the talking as they must charm Sutcliffe and Bill is likely to become angered due to the creature eating the children. Under the guise of "Doctor Disco of the Fairbrook Society", the Doctor meets Sutcliffe who instantly makes sexist, classist but mainly racist, remarks towards Bill even calling her a "creature" and demanding she shows "respect in the presence of [her] betters". In response, the Doctor punches him in the face, knocking the man down, determining that Sutcliffe is very clearly human. Bill agrees that if Sutcliffe was an alien "then that was pretty convincing racism."

Bill and the Doctor are quickly captured by Sutcliffe's minions with a bruised Sutcliffe revealing the creature has been a family secret for years. The Doctor deduces Sutcliffe funded the current fair, as the regular one wasn't able to draw in enough victims for the creature to digest. Sutcliffe plans on blowing up the ice and sinking numerous victims to feed the creature. Bill is confused, as everyone will see it; however, Sutcliffe states the people would be too stupid to notice the creature as they will stop to mourn the ice "breaking". He claims to be moving the world forward by using this new fuel, citing that the lives of those eaten by the creature were not important. However, the Doctor tells him real value is putting an unimportant life above his own. Sutcliffe notes that the speech would have moved anyone with the slightest bit of compassion; he then adds with an evil smirk "not your lucky day, is it?"

The Doctor and Bill are shoved into a carriage by Sutcliffe, who plans on storing them at the fair until he can detonate the ice; not wishing to risk the duo having warned others to stay away, he plans on detonating at noon after he brings in an elephant to draw in a crowd. Sitting in the carriage, Bill wonders if the Doctor really is 2000 years old; he wonders why she asks. With an impressed smile, Bill asks if it takes that long to be able to make a righteous speech like the Doctor did.

Once at the fair, the Doctor and Bill are tied to a pole near the explosives. Bill thinks she can save them by screaming for help; however, the Doctor tells her not to bother. She screams anyway, being drowned out by the people's cheers and the performers. Once done yelling, Bill asks the Doctor what they should do. He asks her to help him get his sonic screwdriver to cut through the ropes they're in. This also attracts the angler fish. Their guard rushes in and the Doctor hands him the sonic causing the fish to become attracted to him and suck him through the ice.

Free, the Doctor tells Bill that they have two choices: let the creature suffer for centuries, or free it. Bill points out that it could kill everyone if let go. However, the Doctor tells her that it's her choice; he works for the human race, and will only do something that could drastically change the future only if he's ordered too. Remembering the creature's moans of agony, Bill tells the Doctor to free it. Knowing people will be harmed, the Doctor tells Bill to save the people on the ice which she does with the help of the urchins, managing to convince everyone the ice is melting to get them off the ice causing Sutcliffe to rush his plans and detonate immediately. However, the Doctor had used his dive suit to plant the explosives around the chains of the sea creature instead, using his sonic to loosen the wires, releasing it. The creature begins to swim away, cracking the ice above it and causing Sutcliffe to fall into the water to his death.

The Doctor pulls Bill off of the ice before she falls through though they are drenched by the creature as it swims to freedom without harming anyone, pleasing Bill as it is no longer in despair. Bill wonders where it will go now; the Doctor believes the fish will end up somewhere cold and try to avoid the human race for the rest of its life. However, she then wonders if they just doomed Greenland. As this is possible, the Doctor promises to check on Greenland in its future to see if the fish lives there now.

Later, Bill and the Doctor invite the urchins to Sutcliffe's home to be fed and cared for with the Doctor amending Sutcliffe's Last Will and Testament so that everything passes to Perry, one of the urchins. Bill, rather annoyed, notes that the Doctor couldn't alter the will to have Kitty as the heir (due to the sexism and racism of the era).

Back in 2017 Nardole enters the Doctor's office at St Luke's University. Placing the tea on the Doctor's desk, he notices that the Doctor is still in period garb. However, the Doctor tries passing his outfit off as his "tea-drinking" clothes. Bill exits the TARDIS, still in her period garb, revealing that the Doctor has broken his oath.. He reminds the Doctor of his vow whilst Bill is surprised that googling the sea creature from 1814 turned up no results. The Doctor explains that humans tend to overlook the inexplicable and that the Frost Fair involved a lot of day drinking. He shows her the headlines which detail Lord Sutcliffe's death and, despite the contestion of inheritance, Perry was eventually deemed the legitimate heir.

The Doctor and Nardole soon toss a coin to decide whether the Doctor keeps his vow and remains on Earth, or Nardole leaves him alone. Using a trick he learned from the con artist, the Doctor wins and presumably goes off in the TARDIS with Bill whilst Nardole checks the vault. As he goes to leave, knocking comes from inside, Nardole refuses to let the entity out before hurrying away looking very worried.

Cast

 * The Doctor - Peter Capaldi
 * Bill - Pearl Mackie
 * Nardole - Matt Lucas
 * Sutcliffe - Nicholas Burns
 * Kitty - Asiatu Koroma
 * Pie-Man - Peter Singh
 * Overseer - Simon Ludders
 * Dowell - Tomi May
 * Spider - Austin Taylor
 * Dottie - Ellie Shenker
 * Harriet - Kishaina Thiruselvan
 * Perry - Badger Skelton

Culture

 * The Doctor refers to the whitewashing in history.
 * He mentions Jesus Christ as an example.
 * Bill mentioned that there were more black people present than shown in movies.
 * A frost fair is being held at the frozen River Thames.
 * The Doctor and Bill encounter an elephant walking past.
 * The frost fair has many activities and performances, notably wrestling, sword swallowing, skittles, cartwheel performers, magicians, ring toss, M. G. Clark Printing Co., souvenir shops, book shops, strongmen, pubs, The Nelson Arms, The City of Moscow and "try your luck" stalls.
 * A map for 19th century London is displayed on the TARDIS scanner.
 * The Doctor reads Struwwelpeter out loud for the street urchins.
 * The Doctor shows Bill the British Newspaper Archives when trying to find information about the frost fair-incident.

Biology

 * Bill refers to the melanin in her skin.

Technology

 * Spider steals the Doctor's sonic screwdriver.
 * A detonator is wired up to explosive barrels.
 * The sonic screwdriver works underwater.
 * The Doctor and Bill wear diving suits.

Science

 * Bill thinks they have travelled to a parallel world.
 * The Doctor says only real wrestling is in zero gravity with tentacles and magic spells.
 * According to the psychic paper, the Doctor works for the Palace. The Doctor says he hasn't heard that one in a while.
 * In Sutcliffe's mansion, the Doctor plays with an Orrery.

Currency

 * The frost fair costs only sixpence to take part.

Food and beverages

 * A bypasser accidentally drops a basket of fruits and vegetables on the Thames.
 * A seller is selling chestnuts just above the stairs to the fair.
 * Food stalls at the fair include:
 * Shish kebab, shish squid, shish chicken, ox cheek, Lapland Mutton, sheep heart etc. stalls.
 * Fish pie, meat pie, chicken pie etc. stalls.
 * Gingerbread stalls.
 * Gin stalls.
 * The Doctor steals fish pies from a con-artist.
 * Nardole has made tea and adds coffee to give it flavour.
 * Sutcliffe has a bowl of nectarines, pears, clementines, grapes and apples.
 * At Sutcliffe's mansion, the street urchins are given a traditional Christmas dinner, consisting of turkey, salad, potatoes, gravy, broccoli, red cabbage, a Christmas pudding and glasses of milk.

Species

 * A giant sea serpent is held chained beneath the Thames. After it broke free, the icy River cracked and ended the frost fair tradition.
 * Lure fish were swimming in the River Thames, luring people out on the thin areas of the ice with their green light bulbs and trap them underneath for the serpent to feed on.
 * The Doctor mentions fireflies and glow worms.
 * The excrement from the sea serpent is used as fuel by Sutcliffe's people.

People

 * The Doctor jokes with Bill about an imaginary person called "Pete" who stepped on a butterfly and got erased from history.
 * The Doctor likes good con artists.
 * Watermen are in charge of keeping order at the frost fair.
 * Bill says she was a skittles champion two years in a row.
 * Sutcliffe is racist and sexist.
 * Sutcliffe has hired dredgers.
 * The workplace has a dredger-in-chief overlooking the work.
 * Sutcliffe has a manservant.
 * Sutcliffe greets the Doctor as "Doctor Disco, from the Fairford Club".
 * The Doctor refer to the sea serpent as "Tiny", "the loch-less monster" and the "not-so-little mermaid".

Locations

 * The TARDIS lands on the Blackfriars Bridge next to New Lime Wharf.
 * The fair stretched from Blackfriars to London Bridge.
 * The Doctor and Bill are heading towards Freezeland Street.
 * Kitty worries that the Doctor will take her and the other urchins to the Magistrate.
 * Sutcliffe has a workhouse upriver where his men work with the serpent's excrement.
 * The Doctor questions whether the chief dredger checked that no one followed the transport carts all the way to Hampton. He says he checks all the way to the steel mill.
 * Bill worries the serpent will eat people off the Southbank and half of London and that they've doomed Greenland.

Story notes

 * The read-through for Thin Ice took place on 18 July 2016, and filming on the episode began on 1 August.
 * Steven Moffat joked in an interview that the intro to EastEnders was always about a giant snake, a reference towards the view of the River Thames from above, which makes it look like a serpent.
 * Spider is one of the few child characters to actually be killed on-screen throughout the history of the program.
 * For shots involving the Doctor falling below the ice in his diving gear were created by The Model Unit using a miniature 1/3 scale puppet inspired by a similar effect in ’s film . To create Capaldi's head, Stephen Mansfield was invited back to the production to sculpt the feature. Mansfield had previously worked on the show during the era of Sylvester McCoy, making such creatures as the Destroyer and the Haemovores. The members of the team who worked on the effect, as listed on the Facebook page of the Model Unit, are:
 * Model Unit Supervisor: Mike Tucker
 * Senior VFX Technician / Sculptor: Alan 'Rocky' Marshall
 * Senior VFX Technician: Colin Mapson
 * Portrait Sculptor: Stephen Mansfield
 * Director: Bill Anderson
 * Producer: Nikki Wilson
 * Line Producer: Steffan Morris
 * Underwater DoP: Rob Franklin
 * Grip: Sam Reeves
 * Gaffer: Mark Hutchings
 * Best Boy: Andy Gardiner
 * Kitty warning Spider about how they'll be transported if caught is a reference to how England would transport convicts to Australia contemporaneously.

Ratings

 * 3.76m (UK overnight figures)
 * 5.61m (UK final)

Filming locations

 * Kings Weston House, Bristol - Sutcliffe Manor

Production errors
to be added

Continuity

 * The Doctor and Bill find themselves in the middle of the frozen River Thames with an elephant crossing their path. (TV: Smile)
 * The Doctor previously visited the 1814 Frost Fair with River Song. They brought Stevie Wonder with them to perform. (TV: A Good Man Goes to War)
 * He mentions having been there before, "a few times". (AUDIO: Frostfire, PROSE: The Frozen, TV: A Good Man Goes to War)
 * He has also previously visited different frost fairs (PROSE: Silhouette, PROSE: The Roundheads) and attempted to visit one other (COMIC: The Instruments of War).
 * The Doctor gives Bill a similar set of directions to the TARDIS wardrobe that the Ninth Doctor gave Rose. (TV: The Unquiet Dead)
 * He doesn't say "third on the left" and "straight ahead".
 * The Doctor wears a hat. This incarnation rarely wears them, having done so only once before. (COMIC: Gangland)
 * According to the short story The Frozen, in February 1814, the Hyban Masoon froze the Thames on arrival.
 * In Regency London, Bill voices her fear that she will be enslaved due to the colour of her skin. Martha Jones voiced the same concern when she visited London of 1599 with the Tenth Doctor. (TV: The Shakespeare Code)
 * Bill speculates that they had travelled to a parallel world. (TV: The Age of Steel)
 * Bill is concerned about the butterfly effect, also exactly like Martha in her first visit to London's past. (TV: The Shakespeare Code)
 * Bill asks about physical side effects of time travel. (TV: The End of the World, Doomsday, The Sound of Drums et al.)
 * The Doctor says he's getting used to being asked how he finds people. (TV: Partners in Crime, The Sontaran Stratagem)
 * The Doctor alters a will again. (TV: The Lodger)
 * The Doctor reminds Bill of her recent experience with death when they visited a garden full of dead people. He confirms this was only a few hours before this episode. (TV: Smile)
 * The Doctor reminds Bill that he is her tutor. (TV: The Pilot)
 * The Doctor asked Bill if she noticed he was "down with the kids" after entertaining the urchins. He previously noted his ability to fit in. (TV: School Reunion)
 * The Doctor has previously used the "conjecture/proposition/conclusion" manner of working out a problem. (TV: Listen, The Witch's Familiar)
 * The Doctor once again notes humanity's habit of overlooking and forgetting the bizarre. (TV: Remembrance of the Daleks, In the Forest of the Night) Charlie Smith noted the same after the Shadow Kin came close to invading Earth through Coal Hill School. (TV: The Coach with the Dragon Tattoo)
 * The Doctor uses his psychic paper. (TV: The End of the World et al.)
 * Nardole reminds the Doctor of his oath. (TV: The Pilot, Smile)
 * Nardole reminds the Doctor he said he wouldn't be going off-world. (TV: Smile)
 * Nardole has made tea for the Doctor. (TV: Smile)
 * Nardole mentions being reassembled. (TV: The Husbands of River Song, The Return of Doctor Mysterio)
 * The Doctor again mentions how you don't steer the TARDIS; you reason with it. (TV: Smile)
 * The Doctor once more states that he's 2,000 years old. (TV: Deep Breath, Smile)
 * The Doctor is asked how many people he has seen die (TV: Journey's End) and personally killed. (TV: The Wheel in Space, State of Decay, TV: The Two Doctors, TV: The End of the World, The Day of the Doctor, The Time of the Doctor, et. al) He remarks on how he has lost count. (TV: The Day of the Doctor)
 * The Doctor mentions how sometimes the options available are limited, and begins to say something about choices, alluding to the explanation he provided to Clara. (TV: Mummy on the Orient Express)
 * Bill questions if the Doctor cares about people dying; Psi had similarly questioned the Doctor's detached nature. (TV: Time Heist)
 * The Doctor punches someone in the face out of anger and defence of his companion. (TV: Hell Bent)
 * Sutcliffe refers to the Doctor as "Doctor Disco". (TV: The Zygon Invasion)
 * The Doctor and Bill return to the Doctor's office. Bill remarks that it looks the exact same, from the cup of previous sonics, wooden raven and family photographs to the books, the busts and the placing of the chairs. (TV: The Pilot)
 * Bill uses search-wise.net to look for the serpent incident. Rose Tyler used the same web to look up the Ninth Doctor. (TV: Rose)
 * Nardole checks on the vault. (TV: The Pilot)
 * Someone behind the vault doors knocks three times repeatedly. The last row of knocks is 4 times. The Doctor previously said knocks were weirdly in rows of 4. (TV: Hell Bent) was previously plagued with a drumming sound in 4 beats, and later a prophecy developed around the Tenth Doctor's death being preceded by 4 knocks. (TV: Utopia/The Sound of Drums/Last of the Time Lords, Planet of the Dead, The Waters of Mars, The End of Time) The Midnight entity also used 2, 3 and 4 knocks when inspecting the Midnight Crusader Tours' shuttle bus. (TV: Midnight)
 * The Doctor once again defers to his human companion's judgement as to whether to allow a creature to live or die. (TV: The Beast Below, Kill the Moon)
 * The Doctor states the sonic screwdriver is sonic because it makes a noise. (TV: The Next Doctor)
 * The TARDIS scanner displays a contemporary map of London (TV: The Visitation)

DVD releases
to be added

Blu-ray releases
to be added

Digital releases
to be added