Harry Potter and the Half-Blood Prince2009

Albus Dumbledore:
Now as you know, each and every one of you was searched upon your arrival here tonight and you have the right to know why. Once there was a young man, who like you, sat in this very hall, walked this castle's corridors, slept under its roofs. He seemed to all the world a student like any other. His name: Tom Riddle. [Murmuring erupts among the students] Today, of course, he's known all over the world by another name, which is why, as I stand looking out upon you all tonight, I'm reminded of a sobering fact: Every day, every hour, this very minute, perhaps, dark forces attempt to penetrate this castle's walls. [pause] But in the end, their greatest weapon... is you. There's something to think about. Now off to bed, pip pip.