Weve all experienced it: that heady rush of excitement when a film just grabs you, right from the beginning, and wont let go. That opening scene, that first act, hooks you, and for a little while youve totally, utterly suspended your disbelief: more than that, youve given your critical and cognitive functions the night off, happy to let the film be your brain for the next two hours. And then it does let go. You dimly emerge from the fog, brain all sleepy for having been woken early and as the film goes on, your suspension of disbelief becomes harder to sustain. For whatever reason, youre starting to pick this apart: noticing gaping plot holes, wincing at terrible dialogue, or worse youre just bored. Sometimes the movie is genuinely dull or bad, but with a fantastic set-piece glued to the front sometimes its simply a film of two halves, and the second one sucks. Sometimes the pacing is off, and the movie just loses its way part way through, or runs out of ideas, or has a terrible revelation in act two that ruins everything, or an absolutely godawful ending. Whether its that, or a combination thereof, these are the films that, part way through, have you saying to yourself hang on a minute oh, good grief. And of course, here be spoilers.