you cross the threshold on the way out, then remember a thing, and come back, and cross it again. it is the small came-back that matters — the seam where the leaving folded onto itself. the building noticed.
this means a decision you had thought settled is being offered for reconsideration. not by you and not by anyone in particular: by the room. the matter is small and recoverable. the door is being polite.
when you go out the second time, stop on the threshold for one slow breath. ask yourself whether the thing you forgot was the actual thing. it usually was not. carry on if the answer is yes, or stay home if the answer is no; either is honored.
— field note: three crossings is not this omen. three crossings means you have lost the keys. begin again from the coat.