When you pick up the leather shoe-shaped doorknob, a hole at the south end of the hall lights up. It pulls you to it, snaps inside the hole, which cuts off the piercing light, but the section of wall swings open on hidden hinges.
The room beyond it is well-lit, and yu can see a dragon crouching in the middle of it. The dragon is the same color as the hound in the foyer, though its scales gleam in the torchlight as though they were very recently polished.
Though you may try to retreat back into the hallway, the curse upon the doorknob compels you forward, only releasing once the door and ground shut behind you, once again seamlessly blending into the walls around it.