The TARDIS crew a violently thrown about as they come out of the time vortex into an alternate reality.  In this reality Rose's father is still alive and someone of prominence.  Mickey's dead grandmother is also alive and he goes to see her.  When the Doctor and Rose discover that the earpeices that everyone wears drops info straight into the brain, they go to Rose's father's house to discover more.  Mickey, meanwhile, has been "taken" by some people who have mistaken him for this reality's version, Rickey.  While at the house posing as servants, Rose and the Doctor discover that the secret behind the Cybus Coroporation is new cybernetic advancements - Cybermen.