The Doctor looks and seems human. He's handsome, witty, and could be mistaken for just another man in the street. But he is a Time Lord: a 900 year old alien with 2 hearts, part of a gifted civilization who mastered time travel. The Doctor saves planets for a living – more of a hobby actually, and he's very, very good at it. He's saved us from alien menaces and evil from before time began – but just who is he?