A solar tsunami sends the TARDIS hurtling towards a futuristic factory on Earth, where human Doppelgängers ("Gangers") are used to mine dangerous acid. They use the white clone goo to create avatars, which can safely mine while the actual people are controlling them with their thoughts. The Doctor would much rather have this adventure alone, but Amy and Rory insist on coming along. The factory is dangerous. Dangerous enough, in fact, to dissolve the Doctor's shoes with acid, so he has to borrow a pair of sneakers.