It isn't spelled out in one scene...
I don't feel like explaining it again... Here, read this thread starting with my first post: http://www.killermovies.com/forums/f38/t345091.html Lazerlike knows what he's talking about...
Extra for experts: http://www.killermovies.com/forums/showthread.php?s=&threadid=345772&perpage=20&highlight=&pagenumber=2