Heres what i'd liked to have seen for a back story to it:
You first see the girl outside, then when the player gets to close she goes into the building. Once the player walks in you have to find her, you see her go into a room(The room besides the Rotom room), the player goes in.
In the room you find a book on the floor, the player clicks on it and in text "Its a book full of pictures on the people who lived here." The butler then walks, then walks back out. The Player looks for him and hear something *This is outside Rotoms room*, the player goes in and sees the tv.
*Rotom battle, blah blah blah*
Once the Player beats or Catches Rotom you go out to the main room and find a newpaper in the middle of the floor. The player clicks on it "Top story: Owners of the Chateau Daughter still missing along with the butler. The owners fleed after reported seeing a strange pokemon that took over Appliances chased them out of the building. At the time the Daughter and Butler where in their rooms sleeping."
Once the player gets done a "!" pops up and the screen moves over to the belcony and sees both the little girl and Butler watching the player, then they leave.