What you need to do is go back to the room where the nooses are hanging and pull down the correct one. You somehow figure out which one is right by reading the papers posted on each corpse, and figuring out which one was the innocent, and pulling the corresponding noose in the other room. If your wrong, a couple of those armless-latex-roach-things appear in the hall. I think I just pulled them all down to pass. Hope this makes sence!