Servants' Quarters
Against your own judgment, you open the door. The growl definitely belongs to a dangerous beast but you go into the room anyway. Multiple coat hanger stands on your right as you enter the door. A soft carpet welcomes you as you step in. You take a good scan of the interior. In the center sits a table with some cups and a teapot surrounding some candles. You can smell a faint aroma of herbs in the room. Some potted plants sit withered in the corners of the room. There is a large open closet to your left that is packed with servant uniforms. From the atmosphere of the room, it looks like it is used for receiving guests and serving them while they are waiting.
On the other side of the room is another door. You try the knob and hear a click but when you try to push the door, it does not budge. You try to push the door open again but you can feel a lock still locking the door in place. You look under the knob and see a keyhole.
Believing that the key is somewhere in the room, you search around. The first place you check is the uniforms in the closest. It would make sense for all of the servants in the mansion to have access to the room or at least some of them. You check all of the pockets but you come up with nothing. You check the tables and every compartment in the room but there is no key. It seems that you will have to look elsewhere to find the key.