The Mystery at Shaw School

You've received a letter from your brother, Billy who is away at boarding school. Something doesn't sound right. You know your brother well and it sounds like he is in trouble. You decide to go and visit. On arrival to the school you are escorted to your brothers deserted form room by a prefect who then locks the door behind you! What is going on? Where is everyone? Billy is a smart kid, maybe he's left you some clues...