Very good episode. Starts out typically (Doctor arrives on scene just as something weird begins happening), he had knowledge the others don't about their fates, and must decide what he is or isn't going to do about it. The last 30 minutes was very exciting and dark, and shows us a side of the Doctor I haven't seen since the Christmas episode with the spider lady. Looks like it leads right into the Christmas special. The trailer for that is excellent, with a lot of familiar faces popping up.