The Doctor takes Amy on her first voyage in the TARDIS and it turns out to be a terrifying trip.

They discover that Britain is now a spaceship, named Starship UK. The Time Lord is concerned that it is a police state with chilling monsters the Smilers and cloaked figures called Winders monitoring every movement. He sends Amy off to help a crying girl but as she finds a scorpion-like creature, she is knocked unconscious and when she wakes up she presses a button marked ‘forget’.

Meanwhile, the Doctor meets the enigmatic Liz Ten, played by Sophie Okonedo, who wants him to help her discover why the spaceship is floating without an engine. As he tracks down and rescues Amy, they fall through the floor into the mouth of a vast alien creature under the spacecraft.

After they escape, Liz Ten reveals that she is the queen of the Starship UK. However, it emerges that she too has been made to ‘forget’ the truth that, years before, the Earth was burning and the citizens of the UK were saved by an enslaved Starwhale who has carried the ship on its back ever since.

The Doctor knows if he frees the Starwhale, the population will be destroyed, but as he makes the difficult decision to numb the creature’s senses so that it doesn’t feel its burden, it comes to light that it volunteered for its task and is happy to continue.

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