The BBC's website has a spoilerific summary for the season finale... as I don't watch the show, I didn't understand what it was talking about. Be warned spoilers ahead!
spoiler (click to show/hide)
Earth has been conquered and the Master rules supreme, with the Doctor a helpless prisoner, in the final episode of Russell T Davies's Doctor Who.The entire human race has been reduced to slavery, as the mighty warships of a new Time Lord Empire rise from the ashes. Only Martha Jones can save the world...