"Shouldn't you?" Kaede says quietly, turning her gaze away from Cas. "I just... was going to go down to the classrooms and work on cleaning out the one I picked. I couldn't sleep-" A lie. She can't sleep. Not when every time she closes her eyes some terrifying thing in the darkness is staring back at her. "-so I decided to do something other than sit in my room."

But the 'can't sleep' is obvious - Cas had seen her not long ago and she hadn't had the darkness under her eyes, then.