The door closes behind him and he's out on the street again as he mulls over that.
It wouldn't surprise me, given how old the place is. A seam in a stone wall should still give off a draft, though. Any spell cast as an illusion to obscure or to force your eyes to drift when you might be curious... the entire castle is so saturated in magic it might just be possible to obscure it behind the larger framework of spells and wards.
no subject