Thin Ice (Doctor Who episode)

The Doctor (Peter Capaldi) and Bill Potts (Pearl Mackie) visit the last great frost fair in London 1814, but they soon find that something sinister is lurking below the frozen Thames.

After dressing in period garments, they take time to explore it, unaware the TARDIS sensors have identified a large life form, a kilometre long, under the ice.

Sutcliffe affirms his family has used the creature to amass a fortune by feeding it victims then collecting and selling its waste as a super powerful replacement for coal.

Bill works with Kitty and the other orphans to clear people off the ice, while the Doctor takes the bomb and places it on the creature's chains.

Bill finds from old newspapers that the orphans lived a fulfilling life, though is surprised to discover no mention of the sea creature.

Nardole, while checking the Vault beneath the University, hears something behind it knock repeatedly and promises to prevent its release even if the Doctor is distracted.

[12] Nivea Serrao of Entertainment Weekly also praised the episode generally, as well as Bill and her reaction to her surroundings, and the Doctor's realization that he had seen and caused a lot of death.

He praised the fact that, as "Bill wades deeper into the exciting insanity of the Doctor's lifestyle, she also realizes that it's not all fun and games".

[17] Daniel Jackson from Radio Times gave the episode a full 5 stars, commending the story for its multi-layered structure and exploring the hidden depths in the characters.

He commented on how Sarah Dollard explored the characters and how she "examines his moral code; the ideals he aspires to and the crimes and misdemeanors he's prepared to indulge.