He does not care for the disbelief on your face.
Yes, this is exactly what she is singing. And he is there to whisper the words to her because French is not her first language: these are Italians.
And he is sorry if you do not believe either in anachronism or the backward fluidity of time.
He thinks that perhaps, if you want to be skeptical, you should go despite that she is begging you not to leave her. The shadow of your shadow? The shadow of your hand, of your dog?
How sad you have made her! Go now….
Ne Me Quitte Pas written in 1959 by Jacques Brel, 1929-1978, Belgian and interpreted here by Nina Simone, 1933-2003, American