For instance, if I told you that this episode of Doctor Who holds what may be the best cliffhanger in the history of the show, what would be worth reaching that objective?
Perhaps a rushed first act, in which the story skims through history and last season like a clip montage for the sake of getting the characters where the story needs them to be? Perhaps a disjointed second act, in which each scene barely manages to stumble onto the next for no apparent reason, not to mention hold a number of inconsistencies? Ok, for the sake of internet review ranting, about that last bit, how does anybody stab through a Cyberman AND a wooden door using a sword, and if that is supposed to be explained by the culprit being somehow superhuman, how does nobody notice that? Why does the Doctor ride a horse to Stonehenge but then sends River back to the TARDIS for "equipment"? How do the bad guys extract memories of Rory from Amy's mind in 2006 if Rory has never been born? How in the world does a Cyberman continue to operate in pieces after spitting out the human head from the helmet? Isn't the whole point of Cybermen to operate a robot body using a human brain? If the Cybermen work without a brain in them why do they bother capturing and "assimilating" humans?
Ok, anyway, it's Doctor Who, it rarely makes sense. Only normally it's for the right reasons. Still. But if you put up with all that what you get is a great, great payoff. It's a great reversal that, to be frank, I did consider beforehand but still came as a surprise. It also is a gorgeous reversal of the "Doctor vs the monsters", in which we get to examine that maybe all those races perpetually locked in mortal combat against the Doctor actually think HE is the monster and, given the horrible things he has done both directly and by omission, they probably have a fair point.
Building an episode around a cliffhanger like this has the downside that it will live or die in history by the quality of its second part, but I've said before that crazy cliffhangers in wihch the odds seemed absolutely and ridiculously impossible to beat were my favourite part of the classic series, so I won't pretend I didn't love this one.