Technically it's a twist in the middle. The innocent boy who had a crush on the main character turned out to be hiding a famous architect guy in the middle of a huge, old apartment building. He threw the main character, Sam, in there so she would "learn to प्यार him" and "obey everything he says या die." (It's better than it sounds.) It was kinda sad, I liked that kid. In the end he runs into the building right before they blow it up (aka demolish it) because he regretted it. The girl was saved but the boy commited suicide. 0__o Good movie.
And then there's the ending to The Mist which is just depressing.