Hogfather - Unseen

Susan edged up to the entrance to the stairways and peered around into the point of a crossbow.

'Now, all of you step out where I can see you.' said Peachy conversationally. 'And don't touch that sword, lady. You'll probably hurt yourself.'

Susan tried to make herself unseen, and failed. Usually it was so easy to do that that it happened automatically, usually with embarrassing results. She could be idly reading a book while people searched the room for her. But here, despite every effort, she seemed to remain obstinately visible.

***

Hogfather - p286