- Season 1, Episode 7 - The Long Game
Rose and the Doctor take Adam, who they met in the last episode in 2012, out into the future - the year 200,000. We learn a little about how the Doctor operates - when he goes somewhere, he just asks questions. It doesn't take him long to find out that something is wrong. He expected mankind to be farther along, but something is holding progress back.
They discover they are on Satellite 5, hovering the earth broadcasting all the news. However, someone or something is controlling everything. They observe some strange behavior, and Adam, saying he is overwhelmed, is sent back to the TARDIS.
Where we see that Rose's curiosity is a good human trait, we now see it go wrong in Adam. Instead of retreating to the TARDIS, he explores this strange new world and looks for a way to profit from it. Ah, greed knows no limits of time and space. Sigh.
Rose and the Doctor tap into the Satellite 5 "mainframe" (they apparently still call them that in the future ;-) and find out that while the rest of the satellite is getting colder, floor 500 is hot as blazes. When they investigate, they find out what is controlling everything - a strange violent creature and his human (sort of) henchman. A combination of a friend they met along the way and Adam combine to get them out of trouble, and the three time travelers take the TARDIS back to current day London, to Adam's house to drop him off.
Part of Adam's punishment is being left with an unusual scar - a mind portal device that opens on his forehead - he had it installed on the Satellite to download all of the world's information so he could send it back to himself. This brings up an interesting consequence for time travelers: if they change anything while away and then end up stuck back home, they need to "lay low" and have very dull lives that don't attract attention, or they will be treated as aliens and studied as lab rats. It's not good to mess around with the rules of time travel.