Harry: Tell me about Peter Pettigrew!
Professor Lupin: He was at school witth us, we thought he was our friend.
Harry: No, Pettigrew's dead.
[to Sirius]
Harry: You killed him.
Professor Lupin: No he didn't! I thought so too, until you mentioned seeing Pettigrew on the map.
Harry: The map was lying, then.
Sirius Black: The map never lies! Pettigrew's alive.