A dinosaur materializes in Victorian London and spits out the TARDIS onto the shore of the River Thames. The Doctor (Peter Capaldi) and companion Clara Oswald (Jenna Colman) emerge. The Doctor rests at the residence of the Paternoster Gang: Silurian Reptile Woman Madam Vastra (Neve McIntosh), her wife Jenny Flint (Catrin Stewart), and their bodyguard/butler Sontaran Warrior Strax (Dan Starkey). Madame Vastra confronts Clara about her prejudice against the regenerated Doctor’s new face. The dinosaur bursts into flame through spontaneous combustion, they believe, which the Doctor and Clara investigate.
The next morning, the Doctor roams the street, looking for answers. The Doctor and Clara run across an ad in the newspaper for a restaurant, and each one thinks it was planted by the other. The restaurant is part of a crashed spaceship filled with humanoid robots. Beneath the restaurant lives a sleeping cyborg man with half a face (Peter Fernando), his robot parts replaced over the years by human.
He reveals that he is trying to reach the promised land by replacing his parts, and he killed the dinosaur to get its biological material. He escapes in a hot-air balloon made out of human skin, taking the Doctor with him. The half-face man is suicidal. The Doctor says that if he does not kill himself, the Doctor will kill him to protect the humans. He is impaled on the spire of Big Ben, and the other robots go lifeless. The Doctor thinks the woman in the shop who placed the ad is keeping him and Clara together. Clara is still not sure she can warm to this Doctor, but the previous Doctor (Matt Smith) phones her from the past to encourage her to stay. The half-faced man awakes and meets a woman named Missy (Michelle Gomez), who tells him he has reached the promised land.
The Doctor thinks his new face is familiar because Peter Capaldi had played Caecilius in the Fires of Pompeii episode in 2008. It seems the Doctor liked it and chose it unconsciously when he regenerated. That’s the story, and they’re sticking to it. The cyborg’s ship is the SS Marie Antoinette, sister-ship of the SS Madame de Pompadour from the Girl in the Fireplace episode in 2006. A tramp in the story is played by Brian Miller, widower of Elisabeth Sladen (Sarah Jane Smith). The episode received positive reviews. A kiss between Madame Vastra and Jenny was excised in Singapore. The new opening credits with a kaleidoscope of clock parts was created by fan Billy Hanshaw.
A line about Capaldi’s eyebrows had the readers hysterical in the script read-through. Missy was designed after Mary Poppins, which proves to be ironic later. The mask that Peter Capaldi rips off his face was a very appropriate Matt Smith mask, though that was by accident, and no-one noticed until later. Apparently, the Doctor played guitar in a band with Marcus Aurelius, and it is claimed that many of the exploits of Sherlock Holmes were actually performed by Madame Vastra. The minor plotline about Clara not liking the older face of Peter Capaldi was written to chide fans who felt the same way.