for me it seems that at the superficial level it's about the jealousy.
Bu the last phrase "no open windows ..." makes me think that lyricist is actually one of the partners but he was so distanced from his feeling, that it feels for him that he is watching all the scene from third person point of view.
or maybe he is reliving an old sweet memory of a long forgotten love. he feels everything but he knows nothing is real.
for me it seems that at the superficial level it's about the jealousy. Bu the last phrase "no open windows ..." makes me think that lyricist is actually one of the partners but he was so distanced from his feeling, that it feels for him that he is watching all the scene from third person point of view. or maybe he is reliving an old sweet memory of a long forgotten love. he feels everything but he knows nothing is real.