...They were saved! I laughed with relief - hooray! And the reason I was laughing, the best bit was, it had already been set up. It was completely unexpected, because I'd forgotten about the set up, but the second I saw it I realised I'd been caught. It's like the magician's trick of directing your focus so you don't see him hide the card.
We love it. We love magicians, we love jokes that catch us out, we love getting the murderer wrong when we read detective stories, we love the twist-in-the-tale - so long as we don't guess it. I was very fed up - and it spoilt the book for me - with Salley Vicker's Miss Garnet's Angel because the blurb on the back promised me a stupendous twist I wouldn't see coming. But I did. It seemed so obvious to me, I couldn't believe it was the twist and thought I'd misread the ending. Yet another book using a similar twist - Nicci French's The Memory Game - had me gripped, even though the circumstances are fairly implausible, because it arrived as fresh as it does in Toy Story 3.
If you're writing a big reveal you need to make it plausible as possible, which means you need to set it up nice and early. You need to be consistent with the information you give out and not cheat by withholding stuff, but you also have to have enough exciting stuff going on so the reader doesn't have time to ponder the information you've given them. Give the set-up and then move very swiftly on to something new, something different so the reader gets distracted.
Remember: we want to be surprised, we want to be fooled. Set us up, and catch us out. We love it.