He paused and stepped over to where, standing behind her chair, he shared her point of view.

Even the exaltation of his success did not prevent his impatient wonder why his relation with this girl must always be so uncomfortable.
Then as he stood in silence looking with her, it seemed that he saw with her, and the thing that he had done revealed itself to him for the first time fully, convincingly, with no appeal.

He looked at it with curious, painful interest, but without remorse, even in the knowledge that she saw it too, and suffered.

He realized exultingly that he had done better work than he thought -- he might repent later, but for the moment he could feel nothing but that.

As to the girl before him, she was simply the source and the reason of it--he was particularly glad he had happened to come across her.
He had echoed her talk of disguises, and his words embodied the unconscious perception under which he worked.