Percy recognized the look that passed between Fred and George. It was identical to the expression Ron had been wearing earlier that year, when he decided not to tell Percy about Norbert, and then changed his mind. So he waited politely, and tried not to look forbidding, and sure enough, a moment later the twins joined them at the table. Without preamble, George said, "Professor Quirrell's dead or dying and eating unicorns to stay alive, and we think there's something hidden on the forbidden third floor that he wants and is willing to break into Gringotts and possibly kill people to get."