This is about the collapse of Bowie's persona, Ziggy Stardust. This song closes The Rise and Fall of Ziggy Stardust and the Spiders from Mars and would also mark the climax of the Ziggy Stardust concerts between 1972-1973.
This dramatic and unusual song blends a variety of styles, which Bowie explained in his 2003 interview with Performing Songwriter: "What I enjoyed was being able to hybridize these different kinds of music somewhat. To go from a '50s rock flavored thing with an Edith Piaf nuance on it produced that. There was a sense of French chanson in there. It wasn't obviously a '50s pastiche, even though it had that rhythm that said total '50s. But it actually ends up as being a French chanson. That was purposeful. I wanted that blend, to see if that would be interesting. And it was interesting. Nobody was doing that, at least not in the same way. The same approach was being adopted by a certain number of artists from that era." (This interview is available at Rock's Backpages.)