"We're already there," he snaps-- perhaps it's the use of his name that settles it, but he won't be spoken to in this way, not by a total stranger.

He casts Paralysis, intending to freeze Clarisse in place as he comes into the office and past her to the desk.
"Ask me how I know you don't have Ellie's permission to be here," he drawls, putting his hands on its surface to glare at her, "oh-- never mind. You can't."