Essery didn't get the impression that he was in costume. She was near the doors, having just ushered out the last sleepy Hufflepuff and spending a few moments talking to the Head Girl about who would be taking down the decorations and seeing to the elves, she'd been about to leave herself... when he walked in.
For once, she thought he might not really be noticing what was about him, and she debated leaving anyway... but there was something about the way he was acting that was off. His staying past when he was required to seemed off, really. It made her ... worried. For no reason she could really put words too.
So a few minutes later she was sitting down at her Head of House place at his left, tapping the charmed talons of her fingernails beside his plate. "Take care of your business?" She asked, smiling warmly behind her hideous nose when he looked up.