You go in the mansion, you go up the stairs, and it's there. You can't advance because every time you try to move, the screen wiggles, and you're stuck on that square in front of the stairs. Then you can't go back down the stairs.
That's a puzzle, you need to go in certain order like in Super Mario. But you should be able to leave that corridor if you want to get some of the previous loots, I'll fix it in a patch.
