Harry stuck his head out when he heard the explosion, and feels slightly put out to have been left out of the fun - though his experience of firebombing isn't great. He just puts himself back in his cabin to wait out the chaos.

Later he hears the knocking, and he's not unpleasantly surprised to see the white-haired boy there.

"Pietro," he murmurs, and puts a steady hand on his shoulder to guide him in. "What's happened, eh?"