The Doctor dies. No, seriously, he DIES in the process of stopping Morbius (they fall off a cliff, Holmes-and-Moriarty-style) and the Time Lords can't brings him back because Morbius's defeat is a fixed point in time. And then the episode ends with the Time Lords sending his companion back to Earth. (Where she gets kidnapped by a recurring villain from earlier episodes, but, you know, that's not nearly as epic a cliffhanger as the Doctor's apparent death.) He'll obviously come back in Series Three, but then again, that's why it's such a great cliffhanger! I really want to see how Big Finish handled this scenario compared to how Moffat in the TV series. (They did it first, BTW.)