From Protector of the Grey House:
Natalia sat on the edge of the tub, and watched as the light danced off the mirrors and reflected off the tiles. Her hand tapped on the tile next to her, unnoticed. She thought the low light would confuse the cameras enough. She wanted a little bit of privacy and time to examine the room. In the security room, she deduced Vincent must have a secret room. The entrance was probably in the bathroom, which is why he turned off the security cameras in here. All the doors that led to the bathroom were locked, and the keys were in her pocket. The werewolves and vampires could break down any locked door, which only gained her a minute or two per door. She would have this puzzle figured out before anyone came in, anyway.
Natalia continued to stare at the wall next to the shower, as her fingers tapped out a nervous tune. There was a space of about five feet long next to the shower stall. Most of the walls had something on or against them: shower stall, toilet, sink, shelves or mirrors. That spot was oddly empty. She wondered why she had never thought about it or the large empty area of the second floor beyond Vincent’s room. She realized it didn’t matter. She pushed off the tub and went to the wall, as she wondered what the trick was. There was a door here; she would find it.