The movie is from 2000-2009. English (US).
It involves a lot of mystery and guessing. I remember a character showing another character a room full of antique items ALL of which are fake. Then there's a drawing of a 'fish' as the answer to one of the mysteries.
Finally the antagonist poses as a bus driver driving a bunch of mentally challenged kids to death,so that he can use their healthy organ for his/her sick kid.