When Smith heard a key in the outer door, he recalled that this sound had been one that he had heard somewhat before the last visit of his water brother, so he shifted his metabolism in preparation, in case the sequence occurred again.  He was astonished when the door opened and Jill slipped in, as he had not been aware that the outer door was a door.  But he grokked it at once and gave himself over to the joyful fullness which comes only in the presence of one's own nestlings, one's chosen water brothers, and (under certain circumstances) in the presence of the Old Ones.