Apollo 23
Justin Richards
 The Doctor and Amy arrive at a shopping centre much to The Doctor's disappointment. When arriving they discover that a spaceman has appeared out of thin air. They both decide to materialize to the moon which they successfully do and find the secret Base Diana. Investigating, they learn of a plot by the evil Talerians to take over the Earth by possessing human bodies. The Doctor ends up trapped on Earth and working with secret government officials, manages to return to the moon on Apollo 23, there having secretly been Apollos 18 through 22 before a link was established between Earth and the Moon that allowed instantaneous travel before sabotage caused it to break down, causing the spaceman to appear. On the moon, Amy is captured and possessed and lures the Doctor into a trap, but he manages to escape with the help of Major Calisle who managed to secretly remain unpossesed due to a power failure caused by Amy attempting to stop sabotage. With Calisle's help, the Doctor finds a back-up copy of Amy's personality and restores her to normal and later manages to do the same using the fire suppression system to everyone but the alien leader, Jackson, who had kept his back-up with him. Restoring everyone's minds through their back-ups also erases the alien minds possessing them. Jackson manages to summon an invasion force of actual Talerians and reveals that the real Jackson's experiments had allowed him (the alien possessing him) to transfer himself to Jackson in the first place and start the invasion. The Talerians are revealed to be balloon-like aliens that are extremely fragile and are dying out. They want human bodies to survive. The Doctor restores the real Jackson by secretly giving him his back-up in his tea and he sacrifices himself to destroy the Talerians by shooting out a window, causing a depressurization that kills the Talerian invaders due to their fragility, and also kills him.