"Well Harrikins, there’s another door leading out of the second room, but I didn’t get a good look around because it was about then that the Headmaster showed up," said George. "We tested it a couple more times, and we’re pretty sure that there’s an alert ward on the trapdoor. And possibly on the first door with the Cerberus too. But he’s slower to respond to that being opened. But within one or two minutes of opening the trapdoor, the Headmaster shows up. Even if the Cerberus is unharmed, still in the room, and there’s a Silencing Charm up on the room. And once Snape showed up with the Headmaster, but we’re not sure if that’s a coincidence or not. We suspect he was meeting with the Headmaster at the time and got dragged along."