A Dinosaur in London

In Victorian London, the Pasternoster Gang, comprising of Silurian Madame Vastra, her human maid and wife Jenny Flint, and Sontaran butler Strax, are summoned by the police force when a dinosaur suddenly materialises in the Thames just outside the Houses of Parliament. Madame Vastra observes that the dinosaur has something stuck in its throat, and moments later it spits out the TARDIS onto the banks of the Thames.

Madame Vastra and Jenny announce, to the watching crowd and police, that they will deal with the dinosaur, before heading down to the TARDIS followed by Strax. Strax knocks on the TARDIS door which is opened by The Doctor who is suffering from post-regenerative trauma. As he exits the TARDIS he is closely followed by a confused Clara Oswald. As The Doctor deliriously begins speaking to the dinosaur, and struggles to remember who the people around him are, Clara explains that The Doctor has just regenerated. Overwhelmed, The Doctor then collapses, and the Pasternoster Gang take him and Clara back to their residence leaving the police to erect a containment zone to prevent the dinosaur rampaging through London.

Madame Vastra manages to trick The Doctor into sleeping, while she confronts Clara on her prejudiced attitude to his changed face. Clara admits that she is struggling to adapt to the new Doctor, due to his stark difference to the old one, particularly his apparent age. However, unbeknown to the others in the house The Doctor awakens, on hearing the dinosaur's pleas for help before it spontaneously combusts. He heads down to the river closely followed by his concerned friends. Angry and seeking answers, The Doctor discovers that this is not the first case of spontaneous combustion in London recently, and after spotting a seemingly unfazed man across the river, he jumps into the Thames to begin investigating leaving a very confused Clara - who returns home with the others to start their own investigations hoping they will soon cross The Doctor's path.

TARDIS Arrival

The next morning, The Doctor is roaming the back streets for answers, questioning how his body chooses a new face during regeneration. He steals a man's coat, and finds something of interest in a discarded newspaper. Back at Madame Vastra's house, Clara reads the same newspaper, and discovers a message left for 'The Impossible Girl' directing her towards a restaurant across London.

Believing this message to have come from The Doctor, Clara heads there, where she is reunited with The Doctor. However, he reveals he didn't leave her the message, but before they have time to contemplate who did, they realise that the restaurant is full of robots, who prevent them from leaving. They are then entrapped in their seats and find themselves descending into a lair, where they find the man they saw at the river sitting in a chair surrounded by other, idle human-like robots. The Doctor and Clara realise that this Half-Face Man is in fact a long-lived cyborg, but instead of the conventional human turning themselves into a robot, he is a robot turning himself into a human using body parts taken from the victims of those who then suffered spontaneous combustion so as to hide what has happened to them - including the dinosaur.

The Twelfth Doctor

As the Half-Face Man begins to wake-up The Doctor and Clara try to find away out. However only The Doctor manages to escape. With the other robots now awake Clara finds herself trapped inside and believing that The Doctor has left her to die. Recalling his earlier advice, Clara holds her breath so the robots do not realise she is human. She nearly escapes but collapses from spending too long without air and is caught by the Half-Face Man.

During her interrogation, where Clara is questioned about The Doctor, the Half-Face Man reveals that he is trying to reach the 'promised land' by prolonging his life via parts replacements. Accepting that she is about to die The Doctor reappears, revealing he has been disguised as a robot since his apparent departure. The Pasternoster Gang then arrive and, along with Clara, begin fighting off the robots, while The Doctor chases the Half-Face Man up stairs and back into the main restaurant.

The Half-Face Man then releases a hot-air balloon made of human skin, lifting the restaurant (which is in fact an escape capsule) into the sky with him and The Doctor inside. The Doctor questions the Half-Face Man, who reveals he and parts of the restaurant are from the SS Marie Antoinette, the sister ship to the SS Madame de Pompadour (see "The Girl in the Fireplace") that crash landed on Earth, a long time ago, on a voyage to the 'Promised Land'.

A Confused Doctor

The Doctor forces the Half-Face Man to look at London from above, and warns him that he will either have to kill himself, or he will kill him to protect the human race. Back in the lair, just as the robots close in on Clara and the Pasternoster Gang, the Half-Face Man is seen falling through the sky and is impaled on the spire of Big Ben. The Half-Face Man's death however shuts down the rest of the robots so allowing Clara and the Pasternoster Gang to escape.

After regrouping, Clara finds that The Doctor and the TARDIS have vanished. Fearing she will be stranded in Victorian London Madame Vastra assures Clara that The Doctor will return, pointing out that as she is the person who knows The Doctor best, and that she knows he will return for her. This The Doctor does. However, when she tells him she does not know who he is any longer, he agrees to return her home, but instead they arrive in Glasgow. On exiting the TARDIS Clara's phone begins ringing.

Taking the call, she is shocked to hear the Eleventh Doctor, phoning her from Trenzalore moments before his regeneration from his perspective. He tells her that the new Doctor needs her more than ever, and she agrees to help him adjust to his new body. The Twelfth Doctor, remembering the conversation, asks her whether she will help him, and she agrees to go with him for coffee.

Meanwhile the Half-Face Man awakens in a beautiful garden, and meets a mysterious woman, called Missy, who tells the Half-Face Man that he has reached the Promised Land at last. She also claims that The Doctor is her boyfriend.