Doctor: Matt Smith (Eleventh Doctor)
Companion: Jenna-Louise Coleman (Clara Oswald)
Eve de Leon Allen – Angie Maitland
Kassius Carey Johnson – Artie Maitland
Jason Watkins – Webley
Warwick Davis – Porridge
Tamzin Outhwaite – Captain
Eloise Joseph – Beauty
Will Merrick – Brains
Calvin Dean – Ha-Ha
Zahra Ahmadi – Missy
Aidan Cook – Cyberman
Nicholas Briggs – Voice of the Cybermen
Directed by Stephen Woolfenden
Written by Neil Gaiman
Marcus Wilson (series producer)
Incidental music composer Murray Gold
Series Series 7
Length 45 minutes
Originally broadcast 11 May 2013
The Doctor takes Clara, and her nanny charges, Angie and Artie, to Hedgewick's World of Wonders, an extraterrestrial theme park. They find the park is closed down and under military occupation. The Doctor convinces Captain Alice Ferring that he is an ambassador working for their missing Emperor, and is allowed to stay. They encounter a man named Webley, hiding from the troops, and he shows the visitors his "Webley's World of Wonders", a collection of oddities from across the universe. Deactivated Cybermen are harmless museum pieces, because Cybermen were defeated and exterminated a thousand years ago. He promises a silver "Imperial penny" for defeating one converted into a chess-playing machine, but they discover the operator is really Porridge, a chess champion with dwarfism.
The group prepare to return home, but the Doctor elects to stay and investigate some small metallic insects. The "insects" are Cybermites, which reactivate the Cybermen, who abduct and partially upgrade Webley, Angie, and Artie. Under threat from the reactivated Cyberman army, the Captain reveals that her platoon are incompetent, a punishment unit banished to this planet to keep them out of trouble, and are unfit to defend against Cybermen. Porridge explains the Cybermen were only defeated by blowing up a galaxy occupied by trillions: "blow up" is now the default defence protocol. The Doctor puts Clara in charge of the troops, warning her not to let them destroy the planet while he rescues the children.
The Doctor finds Angie and Artie and is partially upgraded into a Cyberman, sharing the Cyberman super-consciousness, the "Cyberiad". This gives him a split personality as both the Doctor and the "Cyber-Planner", who names himself Mr Clever, share the same body and each control almost half of the brain. The Doctor and Mr Clever agree to play chess for the complete control of the body. Mr Clever is temporarily stopped by the Doctor placing a golden ticket on his face, explaining that the Cybermen's weakness to gold is still present in their current code.
Clara relocates the army to a 'comical castle', an attraction at the theme park, where they take stock of minimal arms: one large anti-Cyberman gun with a limited charge, five hand pulsers, and a planet-imploding bomb. She confiscates the bomb's hand trigger, and forbids Alice to use her assigned verbal command over the bomb. Alice disobeys and attempts to activate it, but is killed by a Cyberman before she can complete the command. The Doctor returns with Angie and Artie, and demands that Clara tie him up to let him finish his chess game, while the army hold off poorly against the Cybermen, who can quickly adapt and upgrade to overcome any obstacle. Mr Clever tricks Clara and destroys the bomb trigger, leaving the group defenceless. Just as Clara and the remaining soldiers are about to be killed, the Doctor manages to distract Mr Clever, claiming that he can win their chess match in three moves. Mr Clever, finding it impossible, diverts the entire three million strong Cyberiad's minds onto the problem, halting the oncoming Cybermen, who have entered the castle.
The Doctor then uses a hand pulser to remove Mr Clever. Angie reveals that Porridge is the Emperor — she recognised him from the imperial penny and waxwork from Webley's World of Wonders, although the artwork portrays him in a more flattering manner than in reality. Porridge/The Emperor activates the bomb verbally and signals for an imperial spaceship to teleport them away. At the Doctor's request, Porridge/The Emperor retrieves the TARDIS just before the planet implodes, destroying the three million Cybermen. Impressed by her intelligence and resourcefulness, Porridge/The Emperor proposes to Clara, who respectfully declines, not wishing to rule the galaxy. The Doctor returns Clara, Angie and Artie home, leaving the Doctor to puzzle over the mystery of the 'impossible girl' while in space a single Cybermite is shown to have survived.