An exploration of 6000 years of yearning, frustrations and sexual fantasies.
The body swap reawakens Crowley's desire on a spiritual level, while being drunk together during the night of Adam's birth did the same to Aziraphale's physical desires. They let themselves indulge in fantasies without acting on the growing tension between them.
Another confrontation by Nina leaves Crowley in an emotional frenzy, flying off on he open street just to get away from London and somehow physically closer to Aziraphale as his longing instincts draw him in.
The first verse is Crowley thinking about Aziraphale, the second half is from the perspective of the new Supreme Archangel.
At first the two are physically shaking with the realization of the other being their salvation. In the end Aziraphale is shaking off the institutionalized salvation of Heaven when the Metatron openly threatens Crowley if Aziraphale does not play along.
Aziraphale flees from Heaven and he and Crowley meet halfway in the sky above Earth: the middle ground.
In the end they finally talk properly and are on the same page with the wants and needs that went unspoken before.
Crowley is surprised and a little overwhelmed at first that Aziraphale actually goes through with kissing him when asked, the same way the demon kissed him in a flurry of emotion right before Aziraphale left. He goes along with the kiss but after so much time apart, drained physically and emotionally, being just together in the confines of their corporations isn't enough anymore. Aziraphale asks to join their true forms and Crowley is more than willing to let go.
When they literally return to their bodies the next morning the supernatural energy and happiness is still radiating strong enough to manifest their wings in human form.