The 11th Doctor has barely recovered from his regeneration before he faces a race against time to save the world after his damaged TARDIS crashes in the garden of orphaned little girl Amelia Pond.

As the Doctor tries to get used to his new body, Amelia tells him about the voices she can hear through a crack in her bedroom wall, and it appears that an alien known as Prisoner Zero has escaped from an intergalactic jail.

The Doctor goes off in his TARDIS, promising to return for Amelia, but when he comes back she is grown up, working as a kissagram and calling herself Amy.

As Amy takes the Doctor to task for his delay, the shape-shifting Prisoner Zero is still making its terrifying presence felt, taking over the bodies of coma patients at the hospital where Amy’s boyfriend Rory works as a nurse.

Alien police force, the Atraxi, are desperate to find Prisoner Zero and threaten to incinerate Earth in 20 minutes unless he is found.

In their bid to save the world, the Doctor and Amy encounter the menacing Zero as it takes on different chilling forms to disguise itself but the Doctor uses a mass computer link-up to finally reveal its true presence.

After a final confrontation with the Atraxi, the Doctor asks Amy to join him on his adventures in the TARDIS, but what is she leaving behind?