The mysterious informant tells the story of how the murderer tricked Yonk to the roof, and then stunned him. Yonk was on the roof when the murderer put some kind of lubricating oil on his shoes and railings, so that the murderer could easily kill him even if he wasn't there at the time. The students of the school gather in the hallway to hear the news of the fourth student's death. They're worried that the school's reputation will be damaged if the school is found out to be responsible for the deaths of four students in a short period of time.