This has to be one of the best thrillers of all time, it was so well crafted and put together. It really amazed me with the amount of time making this movie as perfect as it could be, adding every last touch to make the ending surprising and unexpected, but at the same time making sure to place clues in the film.
I can explain the plot with a simple quote from the movie:
"Once upon a time there was this person named Malcolm. He worked with children. He loved it. He loved it more than anything else. And then one night, he found out that he made a mistake with one of them. He couldn't help that one. And he can't stop thinking about it, he can't forget. Ever since then, things have been different. He's not the same person that he used to be. And his wife doesn't like the person that he's become. They barely speak anymore, they're like strangers. And then one day Malcolm meets this wonderful little boy, a really cool little boy. Reminds him a lot of the other one. And Malcolm decides to try and help this new boy. 'Cause he feels that if he can help this new boy, it would be like helping that other one too."
If you watch it again and you know the twist, you notice the different clues placed in the movie that you would take no notice of the first time. It certainly came as a complete surprise to me, but it ended perfectly in that it satisfied you with everything you need to know. It actually plays back the clues as the character is discovering the 'twist' so it's not easy no get confused.
Definitely worth seeing if you haven't already, Bruce Willis was amazing and Haley J Osment's performance was brilliant. Go see it now!